After updating to Plasma 5.12.1 (beta KWin crashed for me) I can tell things look somewhat nicer and without graphical glitches. Maximizing works fine this time! And Spiral Knights doesn't lock the pointer when it shouldn't. What's still not working right:
- large mouse pointer on Plasma widgets and Wayland applications, normal on title bars and XWayland applications
- same keyboard problems as before
- while there are no more glitches, Plasma widget positioning is still wrong (krunner, Plasma menus, etc...)
- SMPlayer crashes still
At least there doesn't seem to be any regression