I’ve had Kubuntu 24.04 running on my desktop for quite some time now, and I’d noticed there were some system updates recently, so decided to apply them today. IIRC, they included mesa.
Anyway, since the update, when I boot up, the splash screen worked, then the monitors went into sleep mode and nothing was displayed.
I could press Ctrl+Alt+F3 to get a terminal window up, so I removed the splash quiet as is noted when I went looking for solutions, but whilst that now shows more on the boot process, I still can’t get a login screen to come up.
I checked dmesg and the Xorg log file, but there doesn’t seem to be anything obvious.
Are there any other options I can try please?
this thread may be helpful
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Thanks, I tried restarting the kwin_x11 service, and that core-dumped.
The journal reported
qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem
Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb
Adding nomodeset got me a single monitor display back, so I’ve copied off anything important, and I’m just going to rebuild my machine. It’s not ideal, but not sure what else to do
So… I ended up installing Debian for a bit, but I had a few issues with audio, so I’ve now grabbed KDE Neon (which I used to use a while ago).
Seems the installer boots fine, but after install, you get the splash screen, then the displays turn off.
Looking at the settings, it seems that SDDM is trying to boot X11, which if Ubuntu was removing X11 from the distribution wouldn’t work.
I’ve tried modifying the SDDM config file to indicate Wayland (using sddm --example-config >/etc/sddm.conf and updating the DisplayServer property)
I’ve also tried installing several libxcb packages that people have recommended all over the internet. Nothing seems to work. The only way I can get on is using the Ctrl+Alt+F3, log in to the terminal and startplasma-wayland
Trying kwin_x11 with export QT_DEBUG_PLUGINS=1 yields a log where everything seems to load. libxcb-cursor0 is installed.
qt.qpa.xcb: could not connect to display
qt.qpa.plugin: From 6.5.0, xcb-cursor0 or libxcb-cursor0 is needed to load the Qt xcb platform plugin.
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Available platform plugins are: xcb, offscreen, wayland, vkkhrdisplay, vnc, minimal, linuxfb, eglfs, minimalegl, wayland-egl.
How do I either fix the X11 install, or reconfigure SDDM to use wayland?
I’m half tempted to try and find an older Neon ISO running off Ubuntu 24.04, as it’s obviously related to the Ubuntu 25.04 base.