After logging in, the screen is black with only the mouse cursor visible

Help
1

Summary / Solution

The following command and Alexandr_Drobyshevsk’s post resolved the issue for me:
sudo apt purge fonts-katex

Details

Yesterday, I updated Kubuntu on my AMD Ryzen 2200G system. After the update finished, I saw an icon prompting a system reboot. I clicked it, but a crash error appeared and the system wouldn’t reboot. I tried to open Konsole to restart via command line, but it crashed too.

Shortly after, the system became completely unresponsive. I performed a hard reboot using the Magic SysRq key sequence (r,e,i,s,u,b).

After rebooting, the Kubuntu login screen appeared and I logged in. The desktop wallpaper and clock widget showed up for a second, but then the left side of the screen turned green and the right side went black. Only the mouse cursor was visible and responsive.

Assuming it was a graphics driver issue, I gave up on the AMD machine for the moment and switched to another Kubuntu system with an Intel 5500U CPU.

On the Intel system, I downloaded and installed a .deb package for Google Chrome to get some work done. Right after the installation, I saw the same icon prompting a system reboot. After that, almost the same issue occurred. However, this time, the entire screen goes black.

While searching for a solution, I found the KDE forum post linked above. I opened a TTY using Ctrl+Alt+F3, ran sudo apt purge fonts-katex, and rebooted.

The issue on my Intel Kubuntu system appears to be fixed now. I will try the same solution on the AMD system later.

2

That’s plasmashell crashing.

That seems to be kwin crashing, if you don’t have a cursor or any input anymore.
If you still can hit Alt+F2 or Alt+Space to display krunner, that’s also plasmashell crashing.

3

I forgot to mention that the Kubuntu version is 26.04.

That seems to be kwin crashing, if you don’t have a cursor or any input anymore.

Thank you for your response.

On the Intel machine as well, the cursor appeared and responded on the black screen.

I haven’t tried it yet because the AMD machine is currently located far away and I can’t access it right now.

4

maybe im superstitious and there is no basis for this, but two things i always do when the desktop does not come back as expected or seems corrupted.

  • settings > session > start with an empty session
  • delete the entire folder at ~/.cache

then reboot.

and now i’m thinkin this fc-cache -r i’m just learning about might become a 3rd step.

5

hit Alt+F2 or Alt+Space to display krunner

I’m back on my AMD machine.
When I pressed Alt+Space, I heared a system sound that might be “message-new-instant”.

I tried the following:

(Ctrl+Alt+F3 to open a tty)
(enter username)
(enter password)
sudo apt purge fonts-katex
(enter y)
sudo reboot

Now, my AMD Kubuntu 26.04 system seems to be working fine.

6

thank you for this!

can confirm sudo apt purge fonts-katex worked for me!

for reference, I’m running:
Lenovo ThinkPad L14 Gen 3
BIOS Ver: R1YET59W (1.36)
CPU: AMD Ryzen 5 PRO 5675U w/ Radeon Graphics, 2.3GHz
OS: Kubuntu 26.04 LTS
Plasma Ver: 6.6.6.
KDE Frameworks Ver: 6.24.0
Qt Version: 6.10.2
Kernel Version: 7.0.0-34-generic (64-bit)
Graphics Platform: Wayland

7

Adding to this the error I was getting…

KCrash: Application ‘plasmashell’ crashing… crashRecursionCounter=2

kf.package: Could not find required file ‘mainscript’ for package “/usr/share/plasma/plasmoids/org.kde.plasma.iconstasks/” should be QList (“ui/main.qml”)

8

Thank you for your information.
I didn’t know those settings in “KDE System Settings” (I use in Japanese. So, sorry if it have wrong English name.)

By the way, actually, the problem occurred right after installing Google Chrome to my Intel machine, so I deleted it from the Intel machine using the following command.
sudo apt remove google-chrome-stable
Google Chrome is installed my AMD machine too and not removed from the AMD machine.

My Intel machine doesn’t have any important tasks. So I thought I’d like to do a test.
I got “google-chrome-stablecurrentamd.deb”, and I installed it on the Intel machine by Discover again.
I opend Google Chrome, then my system did not break.
Google Chrome version is 154.0.8037.57.
apt search fonts-katex showed that fonts-katex is not installed. (It makes sense because I purged it.)
I tryed to install fonts-kate by apt install fonts-katex.
I opend Google Chrome, then my system did not broke.
I restart my machine, then my system did not broke.

Reinstalling fonts-katex after purging it might be no problem (for now).

Therefore, I wasn’t able to see if the settings you suggested worked, but I’ll remember them for next time—hopefully, it won’t happen again!

9

We’d need a coredumctl output, something like:

coredumpctl debug plasmashell -A "-ex bt -ex quit" |& tee backtrace.txt

And share the backtrace file.

10

I also confirm that the above problem is gone after I purged this font. Also, I did investigate the core dump, and it was clear that plasmshelservice crashed during an attempt to render some text.

11

Here the content of backtrace:

           PID: 2578 (plasmashell)
           UID: 1001 (lyudik)
           GID: 1001 (lyudik)
        Signal: 11 (SEGV)
     Timestamp: Fri 2026-09-25 23:16:10 CEST (12h ago)
  Command Line: /usr/bin/plasmashell --no-respawn
    Executable: /usr/bin/plasmashell
 Control Group: /user.slice/user-1001.slice/user@1001.service/session.slice/plasma-plasmashell.service
          Unit: user@1001.service
     User Unit: plasma-plasmashell.service
         Slice: user-1001.slice
     Owner UID: 1001 (lyudik)
       Boot ID: a7e238695fb14c4c9b0048ccd944348e
    Machine ID: cf5fc6fd4fe046338d76eb06b752357c
      Hostname: mercury
       Storage: /var/lib/systemd/coredump/core.plasmashell.1001.a7e238695fb14c4c9b0048ccd944348e.2578.1790370970000000.zst (inaccessible)
       Message: Process 2578 (plasmashell) of user 1001 dumped core.
                
                Module libgomp.so.1 from deb gcc-14-14.2.0-4ubuntu2~24.04.1.amd64
                Module libsystemd.so.0 from deb systemd-255.4-1ubuntu8.17.amd64
                Module libzstd.so.1 from deb libzstd-1.5.5+dfsg2-2build1.1.amd64
                Module libgcc_s.so.1 from deb gcc-14-14.2.0-4ubuntu2~24.04.1.amd64
                Module libudev.so.1 from deb systemd-255.4-1ubuntu8.17.amd64
                Module libstdc++.so.6 from deb gcc-14-14.2.0-4ubuntu2~24.04.1.amd64
                Stack trace of thread 2578:
                #0  0x00007c7bdfea4028 __GI___pthread_sigmask (libc.so.6 + 0xa4028)
                #1  0x00007c7bdfe4550d __GI___sigprocmask (libc.so.6 + 0x4550d)
                #2  0x00007c7be2b630d4 _ZN6KCrash15setCrashHandlerEPFviE (libKF5Crash.so.5 + 0x60d4)
                #3  0x00007c7be2b656b7 _ZN6KCrash19defaultCrashHandlerEi (libKF5Crash.so.5 + 0x86b7)
                #4  0x00007c7bdfe45330 __restore_rt (libc.so.6 + 0x45330)
                #5  0x00007c7bdf651d51 n/a (libfontconfig.so.1 + 0xbd51)
                #6  0x00007c7bdf6524f7 FcCharSetHasChar (libfontconfig.so.1 + 0xc4f7)
                #7  0x00007c7bdb56b900 n/a (libQt5XcbQpa.so.5 + 0xe4900)
                #8  0x00007c7be0e2a3c3 _ZNK16QFontEngineMulti12stringToCMapEPK5QChariP12QGlyphLayoutPi6QFlagsIN11QFontEngine10ShaperFlagEE (libQt5Gui.so.5 + 0x22a3c3)
                #9  0x00007c7be0e4d895 _ZNK11QTextEngine9shapeTextEi (libQt5Gui.so.5 + 0x24d895)
                #10 0x00007c7be0e6152f _ZN9QTextLine13layout_helperEi (libQt5Gui.so.5 + 0x26152f)
                #11 0x00007c7be26971e5 _ZN17QQuickTextPrivate15setLineGeometryER9QTextLinedRd (libQt5Quick.so.5 + 0x2971e5)
                #12 0x00007c7be2697fc8 _ZN17QQuickTextPrivate15setupTextLayoutEPd (libQt5Quick.so.5 + 0x297fc8)
                #13 0x00007c7be269a1e2 _ZN17QQuickTextPrivate10updateSizeEv (libQt5Quick.so.5 + 0x29a1e2)
                #14 0x00007c7be269b6e3 _ZN17QQuickTextPrivate12updateLayoutEv (libQt5Quick.so.5 + 0x29b6e3)
                #15 0x00007c7bda9f5527 _ZN11QQuickLabel17componentCompleteEv (libQt5QuickTemplates2.so.5 + 0xc3527)
                #16 0x00007c7be210e896 _ZN17QQmlObjectCreator8finalizeER26QQmlInstantiationInterrupt (libQt5Qml.so.5 + 0x30e896)
                #17 0x00007c7be20a02e9 _ZN20QQmlIncubatorPrivate8incubateER26QQmlInstantiationInterrupt (libQt5Qml.so.5 + 0x2a02e9)
                #18 0x00007c7be20a0e20 _ZN17QQmlEnginePrivate8incubateER13QQmlIncubatorP15QQmlContextData (libQt5Qml.so.5 + 0x2a0e20)
                #19 0x00007c7be209a1e4 _ZN13QQmlComponent6createER13QQmlIncubatorP11QQmlContextS3_ (libQt5Qml.so.5 + 0x29a1e4)
                #20 0x00007c7be2c4aa55 _ZN12KDeclarative9QmlObject25createObjectFromComponentEP13QQmlComponentP11QQmlContextRK5QHashI7QString8QVariantE (libKF5Declarative.so.5 + 0xca55)
                #21 0x00007c7be2fa4ff1 n/a (libKF5PlasmaQuick.so.5 + 0x1fff1)
                #22 0x00007c7be2fa5533 n/a (libKF5PlasmaQuick.so.5 + 0x20533)
                #23 0x00007c7be0906343 _ZN7QObject5eventEP6QEvent (libQt5Core.so.5 + 0x306343)
                #24 0x00007c7be176bd45 _ZN19QApplicationPrivate13notify_helperEP7QObjectP6QEvent (libQt5Widgets.so.5 + 0x16bd45)
                #25 0x00007c7be08d8118 _ZN16QCoreApplication15notifyInternal2EP7QObjectP6QEvent (libQt5Core.so.5 + 0x2d8118)
                #26 0x00007c7be08db94b _ZN23QCoreApplicationPrivate16sendPostedEventsEP7QObjectiP11QThreadData (libQt5Core.so.5 + 0x2db94b)
                #27 0x00007c7be0935c0f n/a (libQt5Core.so.5 + 0x335c0f)
                #28 0x00007c7bdf48e635 n/a (libglib-2.0.so.0 + 0x5d635)
                #29 0x00007c7bdf4edbf7 n/a (libglib-2.0.so.0 + 0xbcbf7)
                #30 0x00007c7bdf48dad3 g_main_context_iteration (libglib-2.0.so.0 + 0x5cad3)
                #31 0x00007c7be0935279 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x335279)
                #32 0x00007c7be08d6a7b _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2d6a7b)
                #33 0x00007c7be08df3e8 _ZN16QCoreApplication4execEv (libQt5Core.so.5 + 0x2df3e8)
                #34 0x00005ed3721e1aa3 n/a (plasmashell + 0x2aaa3)
                #35 0x00007c7bdfe2a1ca __libc_start_call_main (libc.so.6 + 0x2a1ca)
                #36 0x00007c7bdfe2a28b __libc_start_main_impl (libc.so.6 + 0x2a28b)
                #37 0x00005ed3721e1bc5 n/a (plasmashell + 0x2abc5)
                
                Stack trace of thread 2580:
                #0  0x00007c7bdf48cbe0 n/a (libglib-2.0.so.0 + 0x5bbe0)
                #1  0x00007c7bdf48e84b n/a (libglib-2.0.so.0 + 0x5d84b)
                #2  0x00007c7bdf4eda8b n/a (libglib-2.0.so.0 + 0xbca8b)
                #3  0x00007c7bdf48dad3 g_main_context_iteration (libglib-2.0.so.0 + 0x5cad3)
                #4  0x00007c7be0935296 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x335296)
                #5  0x00007c7be08d6a7b _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2d6a7b)
                #6  0x00007c7be06da36b _ZN7QThread4execEv (libQt5Core.so.5 + 0xda36b)
                #7  0x00007c7be14cc15b n/a (libQt5DBus.so.5 + 0x1915b)
                #8  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #9  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #10 0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2602:
                #0  0x00007c7bdfe98e51 __futex_abstimed_wait_common64 (libc.so.6 + 0x98e51)
                #1  0x00007c7bdfe9bd6e __pthread_cond_wait_common (libc.so.6 + 0x9bd6e)
                #2  0x00007c7be06e1723 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5 + 0xe1723)
                #3  0x00007c7be06dec5d n/a (libQt5Core.so.5 + 0xdec5d)
                #4  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #5  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #6  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2601:
                #0  0x00007c7bdfe98e51 __futex_abstimed_wait_common64 (libc.so.6 + 0x98e51)
                #1  0x00007c7bdfe9bd6e __pthread_cond_wait_common (libc.so.6 + 0x9bd6e)
                #2  0x00007c7be06e1723 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5 + 0xe1723)
                #3  0x00007c7be06dec5d n/a (libQt5Core.so.5 + 0xdec5d)
                #4  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #5  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #6  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2579:
                #0  0x00007c7bdff1b79d __GI___poll (libc.so.6 + 0x11b79d)
                #1  0x00007c7be2d8b8ca n/a (libxcb.so.1 + 0xc8ca)
                #2  0x00007c7be2d8d28c xcb_wait_for_event (libxcb.so.1 + 0xe28c)
                #3  0x00007c7bdb4fbba0 n/a (libQt5XcbQpa.so.5 + 0x74ba0)
                #4  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #5  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #6  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2582:
                #0  0x00007c7bdff1b79d __GI___poll (libc.so.6 + 0x11b79d)
                #1  0x00007c7bdf4edb4e n/a (libglib-2.0.so.0 + 0xbcb4e)
                #2  0x00007c7bdf48dad3 g_main_context_iteration (libglib-2.0.so.0 + 0x5cad3)
                #3  0x00007c7be0935279 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x335279)
                #4  0x00007c7be08d6a7b _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2d6a7b)
                #5  0x00007c7be06da36b _ZN7QThread4execEv (libQt5Core.so.5 + 0xda36b)
                #6  0x00007c7be21410ca n/a (libQt5Qml.so.5 + 0x3410ca)
                #7  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #8  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #9  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2594:
                #0  0x00007c7bdfe98e51 __futex_abstimed_wait_common64 (libc.so.6 + 0x98e51)
                #1  0x00007c7bdfe9b8cd __pthread_cond_wait_common (libc.so.6 + 0x9b8cd)
                #2  0x00007c7be06e178c _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5 + 0xe178c)
                #3  0x00007c7be2619b04 n/a (libQt5Quick.so.5 + 0x219b04)
                #4  0x00007c7be261c019 n/a (libQt5Quick.so.5 + 0x21c019)
                #5  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #6  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #7  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2596:
                #0  0x00007c7bdff1b79d __GI___poll (libc.so.6 + 0x11b79d)
                #1  0x00007c7bdf4edb4e n/a (libglib-2.0.so.0 + 0xbcb4e)
                #2  0x00007c7bdf48dad3 g_main_context_iteration (libglib-2.0.so.0 + 0x5cad3)
                #3  0x00007c7be0935279 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x335279)
                #4  0x00007c7be08d6a7b _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2d6a7b)
                #5  0x00007c7be06da36b _ZN7QThread4execEv (libQt5Core.so.5 + 0xda36b)
                #6  0x00007c7be2561b8f n/a (libQt5Quick.so.5 + 0x161b8f)
                #7  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #8  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #9  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2597:
                #0  0x00007c7bdfe98e51 __futex_abstimed_wait_common64 (libc.so.6 + 0x98e51)
                #1  0x00007c7bdfe9bd6e __pthread_cond_wait_common (libc.so.6 + 0x9bd6e)
                #2  0x00007c7be06e1723 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5 + 0xe1723)
                #3  0x00007c7be06dec5d n/a (libQt5Core.so.5 + 0xdec5d)
                #4  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #5  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #6  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2599:
                #0  0x00007c7bdfe98e51 __futex_abstimed_wait_common64 (libc.so.6 + 0x98e51)
                #1  0x00007c7bdfe9bd6e __pthread_cond_wait_common (libc.so.6 + 0x9bd6e)
                #2  0x00007c7be06e1723 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5 + 0xe1723)
                #3  0x00007c7be06dec5d n/a (libQt5Core.so.5 + 0xdec5d)
                #4  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #5  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #6  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2600:
                #0  0x00007c7bdfe98e51 __futex_abstimed_wait_common64 (libc.so.6 + 0x98e51)
                #1  0x00007c7bdfe9Failed to open /var/lib/systemd/coredump/core.plasmashell.1001.a7e238695fb14c4c9b0048ccd944348e.2578.1790370970000000.zst: Відмовлено у доступі
bd6e __pthread_cond_wait_common (libc.so.6 + 0x9bd6e)
                #2  0x00007c7be06e1723 _ZN14QWaitCondition4waitEP6QMutex14QDeadlineTimer (libQt5Core.so.5 + 0xe1723)
                #3  0x00007c7be06dec5d n/a (libQt5Core.so.5 + 0xdec5d)
                #4  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #5  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #6  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2603:
                #0  0x00007c7bdff2630f pselect64_syscall (libc.so.6 + 0x12630f)
                #1  0x00007c7bdec1101c n/a (libusbmuxd-2.0.so.6 + 0x401c)
                #2  0x00007c7bdec11d45 n/a (libusbmuxd-2.0.so.6 + 0x4d45)
                #3  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #4  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2581:
                #0  0x00007c7bdfe98e51 __futex_abstimed_wait_common64 (libc.so.6 + 0x98e51)
                #1  0x00007c7bdfe9b8cd __pthread_cond_wait_common (libc.so.6 + 0x9b8cd)
                #2  0x00007c7bd1999edd n/a (libgallium-25.2.8-0ubuntu0.24.04.2.so + 0x599edd)
                #3  0x00007c7bd1965fbb n/a (libgallium-25.2.8-0ubuntu0.24.04.2.so + 0x565fbb)
                #4  0x00007c7bd1999e0c n/a (libgallium-25.2.8-0ubuntu0.24.04.2.so + 0x599e0c)
                #5  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #6  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                
                Stack trace of thread 2612:
                #0  0x00007c7bdff1b79d __GI___poll (libc.so.6 + 0x11b79d)
                #1  0x00007c7bdf4edb4e n/a (libglib-2.0.so.0 + 0xbcb4e)
                #2  0x00007c7bdf48dad3 g_main_context_iteration (libglib-2.0.so.0 + 0x5cad3)
                #3  0x00007c7be0935279 _ZN20QEventDispatcherGlib13processEventsE6QFlagsIN10QEventLoop17ProcessEventsFlagEE (libQt5Core.so.5 + 0x335279)
                #4  0x00007c7be08d6a7b _ZN10QEventLoop4execE6QFlagsINS_17ProcessEventsFlagEE (libQt5Core.so.5 + 0x2d6a7b)
                #5  0x00007c7be06da36b _ZN7QThread4execEv (libQt5Core.so.5 + 0xda36b)
                #6  0x00007c7ba4c2f83f _ZN15KCupsConnection3runEv (libkcupslib.so + 0x2183f)
                #7  0x00007c7be06db674 n/a (libQt5Core.so.5 + 0xdb674)
                #8  0x00007c7bdfe9cb84 start_thread (libc.so.6 + 0x9cb84)
                #9  0x00007c7bdff29ecc __clone3 (libc.so.6 + 0x129ecc)
                ELF object binary architecture: AMD x86-64
12

This issue appears to be similar to the one being discussed in this post.

I successfully reproduced the issue in VirtualBox and took a snapshot while it occurred.

The following command worked:

sudo apt purge fonts-katex

The solution from the linked post also worked for me.
Specifically, the following steps:

(Ctrl+Alt+F3 to open a tty)
(enter username)
(enter password)
fc-cache -r
sudo reboot

I think that the second approach is the smarter approach.

13

I tried deleting the ~/.cache on a broken VirtualBox snapshot, and it worked temporarily. Plasma crashes again when I open Chrome, but even so, being able to use the desktop is a huge help.

While running fc-cache -r seems like a smarter solution for the issue that occurred around Sep. 25, 2026, I’ll keep deleting ~/.cache in mind as a general solution for similar problems.

Unfortunately, Timeshift which is popular among Linux beginner (I think) was not a viable solution for this issue. I’m afraid thousands of new Linux user might give up on using Linux if they can’t get help.

I’ll note down the steps to delete ~/.cache here, as I didn’t know the Ctrl+Alt+F3 command and will probably forget it otherwise.

14

the easiest way to tell if your files are to blame or if the system is borked is to keep a “test” user handy with no changes to any of the defaults.

that way as long as you can get to a tty or SDDM screen you can log in as “test” and see if things look ok.

if so then you know the problem is in your dot files somewhere and deleting .cache is a good first step in figuring out where it issue lies.

now apparently running fc-cache -r is another thing to try.

15

I occasionally have this problem after something crashed, and the next boot seems to stuck on processing cores. sudo rm /var/lib/systemd/coredump/* fixes the problem.

Can’t reproduce now. Will try to generate a core next time it happens.

16

Here is a summary of the workarounds:

  1. General fix (might be temporary):

    • Switch to a TTY (Ctrl+Alt+F3 or F2-F6) and log in.
    • Run: rm -rf ~/.cache (or rm -rf .cache in your home directory)
    • Run: sudo reboot

  2. Better fix for the issue starting around Sept 25 (Google Chrome / Chromium-related):

    • Switch to a TTY (Ctrl+Alt+F3 or F2-F6) and log in.
    • Run: fc-cache -r
    • Run: sudo reboot