Plasma Login Manager crashes on startup due to Qt platform plugins being unavailable

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1

I’m using Plasma Login Manager 6.6.5-1 from Archlinux: Arch Linux - plasma-login-manager 6.6.5-1 (x86_64)

Both plasma-login-greeter and plasma-login-wallpaper are finishing execution due to a SIGABRT, looking into the the coredump from plasma-login-wallpaper using gdb we see:

Core was generated by `/usr/bin/plasma-login-wallpaper'.
Program terminated with signal SIGABRT, Aborted.
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at pthread_kill.c:44
44            return INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
(gdb) thread apply all backtrace full


Thread 1 (Thread 0x7fc9b0407c80 (LWP 1469)):
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at pthread_kill.c:44
        tid = <optimized out>
        ret = 0
        pd = <optimized out>
        old_mask = {__val = {94471523266832}}
        ret = <optimized out>
#1  0x00007fc9b7a3c363 in __pthread_kill_internal (threadid=<optimized out>, signo=6) at pthread_kill.c:89
No locals.
#2  0x00007fc9b79e07d0 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
        ret = <optimized out>
#3  0x00007fc9b79c7681 in __GI_abort () at abort.c:77
        act = {__sigaction_handler = {sa_handler = 0x0, sa_sigaction = 0x0}, sa_mask = {__val = {140504366853770, 94471522913376, 94471522913392, 277, 18090005503353277440, 3, 140504222169584, 140728061366224, 18374403900871474942, 140728061366112, 140504351727398, 277, 18090005503353277440, 18374403900871474942, 18090005503353277440, 3}}, sa_flags = -837054512, sa_restorer = 0x7ffdce1b9480}
#4  0x00007fc9b7f28892 in qAbort () at /usr/src/debug/qt6-base/qtbase/src/corelib/global/qassert.cpp:46
No locals.
#5  qt_maybe_message_fatal<QString&> (msgType=QtFatalMsg, context=..., message=...) at /usr/src/debug/qt6-base/qtbase/src/corelib/global/qlogging.cpp:2169
No locals.
#6  qt_message(QtMsgType, const QMessageLogContext &, const char *, typedef __va_list_tag __va_list_tag *) (msgType=msgType@entry=QtFatalMsg, context=..., msg=msg@entry=0x7fc9b8e02e8a "%s", ap=ap@entry=0x7ffdce1b8fb8) at /usr/src/debug/qt6-base/qtbase/src/corelib/global/qlogging.cpp:412
        buf = {d = {d = 0x55ebdd908c60, ptr = 0x55ebdd908c70 u"This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.\n\nAvailable platform plugins are: eglfs, linuxfb, minimal, minima"..., size = 277}, static _empty = 0 u'\000'}
#7  0x00007fc9b7f296cb in QMessageLogger::fatal (this=this@entry=0x7ffdce1b94c0, msg=msg@entry=0x7fc9b8e02e8a "%s") at /usr/src/debug/qt6-base/qtbase/src/corelib/global/qlogging.cpp:901
        ctxt = {<QMessageLogContext> = {static CurrentVersion = 2, version = 3, line = 0, file = 0x0, function = 0x0, category = 0x7fc9b8dfd0ec "default"}, static DefaultBacktraceDepth = 32, backtrace = std::optional [no contained value]}
        ap = {{gp_offset = 24, fp_offset = 48, overflow_arg_area = 0x7ffdce1b91f0, reg_save_area = 0x7ffdce1b9120}}
#8  0x00007fc9b86df35e in init_platform (pluginNamesWithArguments=..., platformPluginPath=..., platformThemeName=..., argc=@0x7ffdce1b98bc: 1, argv=<optimized out>) at /usr/src/debug/qt6-base/qtbase/src/gui/kernel/qguiapplication.cpp:1368
        fatalMessage = {d = {d = 0x55ebdd8e3d20, ptr = 0x55ebdd8e3d30 u"This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.\n\nAvailable platform plugins are: eglfs, linuxfb, minimal, minima"..., size = 277}, static _empty = 0 u'\000'}
        plugins = {<QListSpecialMethods<QString>> = {<QListSpecialMethodsBase<QString>> = {<No data fields>}, <No data fields>}, d = {d = 0x55ebdd8de9f0, ptr = 0x55ebdd8dea00, size = 2}}
        platformArguments = {<QListSpecialMethods<QString>> = {<QListSpecialMethodsBase<QString>> = {<No data fields>}, <No data fields>}, d = {d = 0x0, ptr = 0x0, size = 0}}
        availablePlugins = {<QListSpecialMethods<QString>> = {<QListSpecialMethodsBase<QString>> = {<No data fields>}, <No data fields>}, d = {d = 0x55ebdd8de770, ptr = 0x55ebdd8de780, size = 11}}
        themeNames = {<QListSpecialMethods<QString>> = {<QListSpecialMethodsBase<QString>> = {<No data fields>}, <No data fields>}, d = {d = 0x55ebdd8e3d20, ptr = 0x55ebdd8e3d30, size = 277}}
        platformIntegrationThemeNames = {<QListSpecialMethods<QString>> = {<QListSpecialMethodsBase<QString>> = {<No data fields>}, <No data fields>}, d = {d = 0x55ebdd8e7d01, ptr = 0x55ebdd8e1770, size = -9223372036854775702}}
        platformIntegration = <optimized out>
#9  QGuiApplicationPrivate::createPlatformIntegration (this=0x55ebdd8dba30) at /usr/src/debug/qt6-base/qtbase/src/gui/kernel/qguiapplication.cpp:1616
        platformPluginPath = {d = {d = 0x0, ptr = 0x0, size = 0}, static _empty = 0 u'\000'}
        platformName = {d = {d = 0x55ebdd8de5b0, ptr = 0x55ebdd8de5c0 "wayland;xcb", size = 11}, static _empty = 0 '\000'}
        platformArguments = {<QListSpecialMethods<QByteArray>> = {<QListSpecialMethodsBase<QByteArray>> = {<No data fields>}, <No data fields>}, d = {d = 0x55ebdd8de950, ptr = 0x55ebdd8de960, size = 1}}
        platformPluginBase = {d = {d = 0x55ebdd8de560, ptr = 0x55ebdd8de570 "xcb", size = 3}, static _empty = 0 '\000'}
        hasWaylandDisplay = <optimized out>
        isWaylandSessionType = <optimized out>
        preferredPlatformOrder = {<QListSpecialMethods<QByteArray>> = {<QListSpecialMethodsBase<QByteArray>> = {<No data fields>}, <No data fields>}, d = {d = 0x55ebdd8de9a0, ptr = 0x55ebdd8de9b0, size = 2}}
        defaultIsXcb = <optimized out>
        xcbPlatformName = {d = {d = 0x55ebdd8de560, ptr = 0x55ebdd8de570 "xcb", size = 3}, static _empty = 0 '\000'}
        defaultIsWayland = <optimized out>
        waylandPlatformName = {d = {d = 0x55ebdd8de4d0, ptr = 0x55ebdd8de4e0 "wayland", size = 7}, static _empty = 0 '\000'}
        platformExplicitlySelected = <optimized out>
        platformNameEnv = {d = {d = 0x0, ptr = 0x0, size = 0}, static _empty = 0 '\000'}
        platformThemeName = {d = {d = 0x55ebdd8de500, ptr = 0x55ebdd8de510 u"kde", size = 3}, static _empty = 0 u'\000'}
        icon = {d = {d = 0x0, ptr = 0x0, size = 0}, static _empty = 0 u'\000'}
        j = <optimized out>
#10 0x00007fc9b87aa9e8 in QGuiApplicationPrivate::createEventDispatcher (this=<optimized out>) at /usr/src/debug/qt6-base/qtbase/src/gui/kernel/qguiapplication.cpp:1634
No locals.
#11 0x00007fc9b8017ce5 in QCoreApplicationPrivate::init (this=this@entry=0x55ebdd8dba30) at /usr/src/debug/qt6-base/qtbase/src/corelib/kernel/qcoreapplication.cpp:865
        q = <optimized out>
        thisThreadData = 0x55ebdd8d6e90
#12 0x00007fc9b87aaaeb in QGuiApplicationPrivate::init (this=0x55ebdd8dba30) at /usr/src/debug/qt6-base/qtbase/src/gui/kernel/qguiapplication.cpp:1667
        loadTestability = <optimized out>
        pluginList = {<QListSpecialMethods<QByteArray>> = {<QListSpecialMethodsBase<QByteArray>> = {<No data fields>}, <No data fields>}, d = {d = 0x7fc9b9e2ef40 <QtPrivate::QMetaTypeInterfaceWrapper<QIterable<QMetaSequence> >::metaType>, ptr = 0x70, size = 140728061368160}}
        session_id = {d = {d = 0x55ebdd8daab8, ptr = 0x60 <error: Cannot access memory at address 0x60>, size = 140728061368224}, static _empty = 0 u'\000'}
        session_key = {d = {d = 0x55ebdd8daaa0, ptr = 0x70 <error: Cannot access memory at address 0x70>, size = 140728061368128}, static _empty = 0 u'\000'}
        s = {d = {d = 0x18, ptr = 0x7ffdce1b9780 u"玐\xdd8d嗫", size = 140504382321952}, static _empty = 0 u'\000'}
        j = <optimized out>
        envPlugins = {d = {d = 0x0, ptr = 0x0, size = 0}, static _empty = 0 '\000'}
        q = <optimized out>
#13 0x00007fc9b87a1e4e in QGuiApplication::QGuiApplication (this=<optimized out>, argc=<optimized out>, argv=<optimized out>, this=<optimized out>, argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/qt6-base/qtbase/src/gui/kernel/qguiapplication.h:175
No locals.
#14 0x000055ebdb1ad747 in WallpaperApp::WallpaperApp (this=0x7ffdce1b9920, argc=@0x7ffdce1b98bc: 1, argv=0x7ffdce1b9b08) at /usr/src/debug/plasma-login-manager/plasma-login-manager-6.6.5/src/frontend/wallpaper/wallpaperapp.cpp:29
No locals.
#15 main (argc=<optimized out>, argv=0x7ffdce1b9b08) at /usr/src/debug/plasma-login-manager/plasma-login-manager-6.6.5/src/frontend/wallpaper/main.cpp:20
        format = {d = 0x55ebdd8db9e0}
        app = {<QGuiApplication> = {<QCoreApplication> = {<QObject> = {_vptr.QObject = 0x7fc9b8f38b80 <vtable for QGuiApplication+16>, static staticMetaObject = {d = {superdata = {direct = 0x0}, stringdata = 0x7fc9b83bed50 <_ZN7QObject32qt_staticMetaObjectStaticContentIN12_GLOBAL__N_125qt_meta_tag_ZN7QObjectE_tEEE.lto_priv.0+272>, data = 0x7fc9b83bec40 <_ZN7QObject32qt_staticMetaObjectStaticContentIN12_GLOBAL__N_125qt_meta_tag_ZN7QObjectE_tEEE.lto_priv.0>, static_metacall = 0x7fc9b807f370 <QObject::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, metaTypes = 0x7fc9b8512980 <_ZN7QObject36qt_staticMetaObjectRelocatingContentIN12_GLOBAL__N_125qt_meta_tag_ZN7QObjectE_tEEE.lto_priv.0>, extradata = 0x0}}, d_ptr = {d = 0x55ebdd8dba30}}, static staticMetaObject = {d = {superdata = {direct = 0x7fc9b8512a20 <QObject::staticMetaObject>}, stringdata = 0x7fc9b837efe8 <_ZN16QCoreApplication32qt_staticMetaObjectStaticContentIN12_GLOBAL__N_135qt_meta_tag_ZN16QCoreApplicationE_tEEE.lto_priv.0+392>, data = 0x7fc9b837ee60 <_ZN16QCoreApplication32qt_staticMetaObjectStaticContentIN12_GLOBAL__N_135qt_meta_tag_ZN16QCoreApplicationE_tEEE.lto_priv.0>, static_metacall = 0x7fc9b801d810 <QCoreApplication::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, metaTypes = 0x7fc9b8512400 <_ZN16QCoreApplication36qt_staticMetaObjectRelocatingContentIN12_GLOBAL__N_135qt_meta_tag_ZN16QCoreApplicationE_tEEE.lto_priv.0>, extradata = 0x0}}, static self = 0x7ffdce1b9920}, static staticMetaObject = {d = {superdata = {direct = 0x7fc9b8512480 <QCoreApplication::staticMetaObject>}, stringdata = 0x7fc9b8e2162c <_ZN15QGuiApplication32qt_staticMetaObjectStaticContentIN12_GLOBAL__N_134qt_meta_tag_ZN15QGuiApplicationE_tEEE.lto_priv.0+780>, data = 0x7fc9b8e21320 <_ZN15QGuiApplication32qt_staticMetaObjectStaticContentIN12_GLOBAL__N_134qt_meta_tag_ZN15QGuiApplicationE_tEEE.lto_priv.0>, static_metacall = 0x7fc9b87b7270 <QGuiApplication::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, metaTypes = 0x7fc9b8f354c0 <_ZN15QGuiApplication36qt_staticMetaObjectRelocatingContentIN12_GLOBAL__N_134qt_meta_tag_ZN15QGuiApplicationE_tEEE.lto_priv.0>, extradata = 0x0}}}, static staticMetaObject = {d = {superdata = {direct = 0x7fc9b8f35ec0 <QGuiApplication::staticMetaObject>}, stringdata = 0x55ebdb1c2dcc <WallpaperApp::qt_staticMetaObjectStaticContent<(anonymous namespace)::qt_meta_tag_ZN12WallpaperAppE_t>+140>, data = 0x55ebdb1c2d40 <WallpaperApp::qt_staticMetaObjectStaticContent<(anonymous namespace)::qt_meta_tag_ZN12WallpaperAppE_t>>, static_metacall = 0x55ebdb1b94b0 <WallpaperApp::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>, relatedMetaObjects = 0x0, metaTypes = 0x55ebdb1c7140 <WallpaperApp::qt_staticMetaObjectRelocatingContent<(anonymous namespace)::qt_meta_tag_ZN12WallpaperAppE_t>>, extradata = 0x0}}, m_wallpaperPackage = {_vptr.Package = 0x7ffdce1b9a10, d = {<QSharedDataPointerBase<QExplicitlySharedDataPointer, KPackage::PackagePrivate>> = {d = {ptr = 0x55ebdd8d64f0}}, <No data fields>}}, m_windows = {<QListSpecialMethods<WallpaperWindow*>> = {<QListSpecialMethodsBase<WallpaperWindow*>> = {<No data fields>}, <No data fields>}, d = {d = 0x1e, ptr = 0x55ebdb1c8658 <orgkdeplasmaloginwallpaperRegistration>, size = 30}}}

Similarly, I see the same message when analyzing plasma-login-greeter about not being able to initialize any Qt platform plugin.

I’m wondering if this issue a code issue, or did if it’s a problem with my configuration (I simply disabled the SDDM service and enabled plasma-login one).

I can provide more data if needed about the coredumps as needed.

Thank you for your time

2

Looks like a packaging issue.

The package hasn’t been recompiled with the right dependency since the last Qt version was updated or something like this.

Did you reboot since you updated ?

3

This happens on every boot. I did try 3 weeks ago with 6.6.4 and the behaviour was the same, although I did not inspect the backtraces.

I’ll open an issue on the arch Linux tracker about this.

Thanks

4

I’m waiting to get my account in arch activated.

In the meantime I tried plasmalogin manually from a TTY:

$ systemctl stop sddm
$ systemctl start sddm

With this plasmalogin starts up just fine and I’m able to login as normally, so I don’t think it’s a matter of a mismatch in the Qt version. I’ll keep investigating to see what might cause this

5

That is not plasma login that is sddm and should stay disabled if you want to use plasma login (at least according to almighty archwiki :innocent: the Plasma Login Manager service should be called plasmalogin not sddm. But personally I still use sddm, never tried plasma login so far).

6

Sorry, that was a typo when I wrote the message, it’s actually

systemctl start plasmalogin

It’s quite noticeable it was different from sddm because the background and theme changed.

And just to double-check I didn’t miss anything

$ systemctl status sddm
○ sddm.service - Simple Desktop Display Manager
     Loaded: loaded (/usr/lib/systemd/system/sddm.service; enabled; preset: disabled)
    Drop-In: /etc/systemd/system/display-manager.service.d
             └─plymouth.conf
     Active: inactive (dead) since Thu 2026-05-14 18:38:08 BST; 30min ago
[...]

$ systemctl status plasmalogin
● plasmalogin.service - Plasma Login Manager
     Loaded: loaded (/usr/lib/systemd/system/plasmalogin.service; disabled; preset: disabled)
     Active: active (running) since Thu 2026-05-14 18:38:30 BST; 30min ago
[...]
7

After reenabling the service again, I’ve managed to make it start up once without issues, while most of the time I simply get a black screen. I’ve discovered that pressing ctrl+c makes the login to appear just fine.

This matches the report in https://bugs.kde.org/show_bug.cgi?id=519134 I’ve added the plasmalogin user to the groups and this still happens, so it doesn’t appear to be fixed yet in 6.6.5, contrary to what the issue states