Created attachment 129383 [details]
the task switcher in one of the odd states described in the bug

Sorry for the lack of specificity: the exact behavior varies between sessions and I couldn't pinpoint how to trigger the same bug on another machine.

SUMMARY

Switching applications with alt-tab has become tricky: often, the switcher displays a single entry for "Show Desktop" (even if the option to include Show Desktop is unchecked).

Sometimes, the switcher appears with transparent background or other rendering artifacts. I haven't been able to reproduce this in a couple of weeks.

When I hit alt-tab and release it, the desktop is indeed revealed.

When I hit alt-tab again, sometimes the windows come back, and sometimes they start coming back, but as soon as I release alt-tab the desktop is shown again.

STEPS TO REPRODUCE

No idea! It just started happening 1 month ago, and I tried selecting different visualizations and fiddling with the other settings, to no use.

However, this is what I know:
 - I can only reproduce this on my Arch Linux box, not on Fedora 32
 - It is unrelated to using 30bpp
 - The bug shows with or without compositing
 - I think it first appeared when I upgraded to qt 5.15
 - I had this bug with plasma 5.18.x, and upgrading to 5.19 didn't fix it
 - It happened with KF 5.70 and KF 5.71
 - Also happens with kwinft built from git master
 - I checked for conflicting shortcuts, and there aren't any


SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.19
KDE Frameworks Version: 5.71
Qt Version: 5.15