Created attachment 143792 [details]
plasmashell output

SUMMARY
The plasmashell process hangs forever on Wayland, resulting in a black screen. Programs can still be launched using key bindings and KWin seems to be working correctly. Killing plasmashell and running it again doesn't help.
X11 session works normally.

STEPS TO REPRODUCE
1. Install the 'plasma-workspace-wayland' package.
2. Restart SDDM.
3. Login into the Wayland session.

OBSERVED RESULT
Black screen.

EXPECTED RESULT
Plasma desktop.

SOFTWARE/OS VERSIONS
Operating System: Debian GNU/Linux
KDE Plasma Version: 5.23.3
KDE Frameworks Version: 5.88.0
Qt Version: 5.15.2
Kernel Version: 5.15.0-3.2-liquorix-amd64 (64-bit)
Graphics Platform: X11
Processors: 4 × Intel® Core™ i5-2400 CPU @ 3.10GHz
Memory: 11.7 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 660/PCIe/SSE2

Nvidia driver version: 470.86-1
Kernel cmdline: audit=0 intel_pstate=disable acpi_enforce_resources=lax BOOT_IMAGE=/boot/vmlinuz-5.15.0-3.2-liquorix-amd64 root=UUID=9a3e5c87-88e3-41d8-9199-8bcaf7dd193f ro reboot=pci quiet splash nvidia-drm.modeset=1

ADDITIONAL INFORMATION
This only happens on my machine with Nvidia proprietary drivers, it doesn't happen on another machine with Intel iGPU.
Wayland session worked (badly, but at all) on this machine before. I believe it broke after the upgrade to 5.23.
Also tested on the stock Debian kernel (linux-image-5.15.0-1-amd64).
Attached: the output of plasmashell launched after killing the original process started by SDDM, hopefully it contains some useful information.