SUMMARY


STEPS TO REPRODUCE
1. In Kate, open a file, edit it, and then close it without saving
2. a popup shows up asking whether or not to exit without saving
3. Hit Cancel

You can observe the issue with any other application, by performing any action that causes a popup to show up, and then closing the popup with any action that does not close the main application (doesn't have to be cancel: in another context selecting ok may close the popup and do whatever you have confirmed to do without closing the application).

OBSERVED RESULT

When the popup shows up on top of the application window, the application window becomes greyed out. When you close the popup, the window gets un-greyed out with a short animation, but it flickers: it does the full animation where it goes from dark to bright, then it goes full dark for one frame and bright again immediately. It's very annoying and it gives the impression that something is broken (well, actually it is)

EXPECTED RESULT

Should do the animation smoothly

Operating System: openSUSE Tumbleweed 20210612
KDE Plasma Version: 5.22.0
KDE Frameworks Version: 5.82.0
Qt Version: 5.15.2
Kernel Version: 5.12.9-1-default (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-1065G7 CPU @ 1.30GHz
Memory: 7.3 GiB of RAM
Graphics Processor: Mesa DRI Intel® Iris® Plus Graphics

ADDITIONAL INFORMATION

This has appeared recently in OpenSUSE Tumbleweed.