SUMMARY
Any Qt apps, including the plasma-shell and SDDM crashes without setting the following environment variables manually: 

QT_PLUGIN_PATH=/usr/lib/qt6/plugins
QML2_IMPORT_PATH=/usr/lib/qt6/qml

Previously, it was working fine, I suspect this happened after an update. I set these variables in `/etc/environment` temporarily as a workaround, as it causes Qt apps that use other installations to crash similarly.

Login via GDM into Gnome desktop works fine, but KDE apps still won't work without setting these variables. 

STEPS TO REPRODUCE
1. Boot the system.
2. Login to Plasma

OBSERVED RESULT
No desktop. Qt paths are not found by apps automatically.

EXPECTED RESULT
Desktop. Apps can find plugin paths automatically.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux
KDE Plasma Version: 6.5.2 
KDE Frameworks Version: 
Qt Version: 6.10.0

ADDITIONAL INFORMATION
SDDM crash log in case it is useful.

```
Kas 15 09:42:24 bilal-pc systemd[1]: Started Authorization Manager.
Kas 15 09:42:24 bilal-pc polkitd[1209]: Acquired the name org.freedesktop.PolicyKit1 on the system bus
Kas 15 09:42:25 bilal-pc sddm-helper-start-wayland[1141]: Directory "/run/user/615" has changed, checking for Wayland socket
Kas 15 09:42:25 bilal-pc sddm-helper-start-wayland[1141]: Directory "/run/user/615" has changed, checking for Wayland socket
Kas 15 09:42:25 bilal-pc sddm-helper-start-wayland[1141]: Directory "/run/user/615" has changed, checking for Wayland socket
Kas 15 09:42:25 bilal-pc sddm-helper-start-wayland[1141]: Found Wayland socket "/run/user/615/wayland-0"
Kas 15 09:42:25 bilal-pc sddm-helper-start-wayland[1141]: "Accepting client connections on sockets: QList(\"wayland-0\")\n"
Kas 15 09:42:25 bilal-pc gjs[1140]: JS LOG: current connection: null
Kas 15 09:42:25 bilal-pc sddm-greeter-qt6[1230]: High-DPI autoscaling Enabled
Kas 15 09:42:25 bilal-pc sddm-greeter-qt6[1230]: Could not find the Qt platform plugin "wayland" in ""
Kas 15 09:42:25 bilal-pc sddm-greeter-qt6[1230]: This application failed to start because no Qt platform plugin could be initialized. Re>
Kas 15 09:42:25 bilal-pc systemd-coredump[1238]: Process 1230 (sddm-greeter-qt) of user 615 terminated abnormally with signal 6/ABRT, pr>
Kas 15 09:42:25 bilal-pc systemd[1]: Created slice Slice /system/drkonqi-coredump-processor.
Kas 15 09:42:25 bilal-pc systemd[1]: Created slice Slice /system/systemd-coredump.
Kas 15 09:42:25 bilal-pc systemd[1]: Started Process Core Dump (PID 1238/UID 0).
Kas 15 09:42:25 bilal-pc systemd[1]: Started Pass systemd-coredump journal entries to relevant user for potential DrKonqi handling.
Kas 15 09:42:25 bilal-pc dockerd[1107]: time="2025-11-15T09:42:25.105826191-08:00" level=info msg="Loading containers: start."
Kas 15 09:42:25 bilal-pc kernel: Initializing XFRM netlink socket
Kas 15 09:42:25 bilal-pc systemd-coredump[1242]: [🡕] Process 1230 (sddm-greeter-qt) of user 615 dumped core.
                                                 
                                                 Stack trace of thread 1230:
                                                 #0  0x00007faa09e9890c n/a (libc.so.6 + 0x9890c)
                                                 #1  0x00007faa09e3e3a0 raise (libc.so.6 + 0x3e3a0)
                                                 #2  0x00007faa09e2557a abort (libc.so.6 + 0x2557a)
                                                 #3  0x00007faa0a69348c n/a (libQt6Core.so.6 + 0x9348c)
                                                 #4  0x00007faa0a694250 _ZNK14QMessageLogger5fatalEPKcz (libQt6Core.so.6 + 0x94250)
                                                 #5  0x00007faa0b0e5fed n/a (libQt6Gui.so.6 + 0xe5fed)
                                                 #6  0x00007faa0b19f438 _ZN22QGuiApplicationPrivate21createEventDispatcherEv (libQt6Gui.>
                                                 #7  0x00007faa0a76ea05 _ZN23QCoreApplicationPrivate4initEv (libQt6Core.so.6 + 0x16ea05)
                                                 #8  0x00007faa0b19f4ce _ZN22QGuiApplicationPrivate4initEv (libQt6Gui.so.6 + 0x19f4ce)
                                                 #9  0x00007faa0b1a068e _ZN15QGuiApplicationC2ERiPPci (libQt6Gui.so.6 + 0x1a068e)
                                                 #10 0x00005579106dfaf1 n/a (/usr/bin/sddm-greeter-qt6 + 0x13af1)
                                                 #11 0x00007faa09e27635 n/a (libc.so.6 + 0x27635)
                                                 #12 0x00007faa09e276e9 __libc_start_main (libc.so.6 + 0x276e9)
                                                 #13 0x00005579106e29e5 n/a (/usr/bin/sddm-greeter-qt6 + 0x169e5)
                                                 ELF object binary architecture: AMD x86-64
Kas 15 09:42:25 bilal-pc sddm-helper-start-wayland[1141]: wayland greeter finished 6 QProcess::CrashExit
Kas 15 09:42:25 bilal-pc sddm-helper-start-wayland[1141]: quitting helper-start-wayland
Kas 15 09:42:25 bilal-pc sddm-helper-start-wayland[1141]: Stopping... "kwin_wayland"
```