Can't boot Plasma Wayland session from Display manager

After updating the system yesterday, it refuses to boot to wayland session. When selecting “Plasma (Wayland)” in SDDM and logging in, it blanks out and shows login screen again.

Looking through journalctl, the following lines got my attention:

ноя 17 20:16:35 wexPC kaccess[1030]: Got keys from plugin meta data ("xcb")
ноя 17 20:16:35 wexPC kaccess[1030]: QFactoryLoader::QFactoryLoader() checking directory path "/usr/bin/platforms" ...
ноя 17 20:16:35 wexPC kaccess[1030]: loaded library "/usr/lib/qt/plugins/platforms/libqxcb.so"
ноя 17 20:16:35 wexPC kaccess[1030]: qt.qpa.xcb: could not connect to display
ноя 17 20:16:35 wexPC kaccess[1030]: qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
ноя 17 20:16:35 wexPC kaccess[1030]: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Here’s full journalctl log with QT_DEBUG_PLUGINS=1: https://0x0.st/oIgv.txt
Can boot normally to xorg though. Also works when starting plasma using startplasma-wayland on multi-user.target.
Not sure how to solve it, would appreciate some help here. Thanks!

Try setting QT_QPA_PLATFORM=wayland. That being said, that should be totally not needed in plasma. It seems something is wrong in your install somewhere.

Definitely not set here, unset it.

This points towards SDDM for the problem. Check journal on sddm, and also sddm logs (if you can find them :smiley: ) ~/.local/share/sddm/

~/.local/share/sddm/wayland-session.log

Error: could not determine $DISPLAY.
Error: Can not contact kdeinit5!
org.kde.startup: "kdeinit5_shutdown" () exited with code 255
startplasma-wayland: Shutting down...
startplasmacompositor: Shutting down...
startplasmacompositor: Done.

From the journal log, it seems sddm is working fine, though wayland crashes after a while loading kde-wayland. I could not see exactly what causes this. I am sorry.

Please, post a list with the upgraded packages (/var/log/pacman.log part).

If you have Gnome installed (or other wayland session), try to log in.

After a pretty long trial and error, i figured it was a problem with AUR package cloudflare-warp-bin, specifically its tray applet that was loading through Systemd service. Boots like usual with it disabled. It worked fine before the upgrade, so that’s weird.
On Gnome Wayland it boots normally too. So is that a Plasma bug? KWin? Should it be reported?

I would first go to that specific package devs and report it. KDE devs would know better, but I wouldn’t expect a quick answer, with all KDE bugs flying around. :person_shrugging: