Running firefox under plasma with kernel 5.15.4 on my rpi 4b has no gui
visible. htop shows it appears to be running normally.

Firefox works under plasma if I switch back to 5.10.78
Firefox works under gnome with either kernel.

I also noticed that right clicking on the title bar of gkrellm, which works
normally under 5.10.78 doesn't display the menu under 5.15.4, but a single
line of pixels turns white at the top left of the screen, suggesting the menu
is opening, but is off screen.

Other applications such as gnome-calculator and konversation work ok with either
desktop environment and either kernel.

Only errors I can find that with 5.15.4 that are not present with 5.10.78 ...
/var/log/Xorg.0.log has one error line with ...
[    57.715] (EE) modeset(0): glamor initialization failed
and dmesg has one line with ...
[   11.149649] Error: Driver 'simple-framebuffer' is already registered, aborting...