SUMMARY
This issue is similar to https://bugs.kde.org/show_bug.cgi?id=426069 , but it is harder to reproduce, which is why I delayed this report. In addition, I'm not sure this issue occurs only with XWayland apps. I've also been affected by this bug for a few months. Both issues might be related.

Sometimes cycling between virtual desktops containing one maximized application each via keyboard shortcut makes the application be rendered, but impossible to interact with. This includes keyboard focus and mouse clicks, although attempting to move it by dragging the titlebar does move it properly. Any attempts to change its window state (maximize, restore etc) shows the respective visual effects, but does not nulify this issue.

This issue has most notably occurred with Telegram, WPS Office and Chromium.

STEPS TO REPRODUCE
1. Create three virtual desktops in a wayland session, easiest to reproduce with them in line
2. Have one maximized application in each of them, wherein each application shows a blinking text cursor
3. Cycle between them using a keyboard shortcut
4. Unlike the linked bug report, this one requires more attention as you may only notice it when the cursor blinking stops, and it's more difficult to reproduce

OBSERVED RESULT
Window can be seen, but can't be interacted with

EXPECTED RESULT
Window can be seen and should be interactive

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20200823
KDE Plasma Version: 5.19.80
KDE Frameworks Version: 5.74.0
Qt Version: 5.15.0