Since upgrading to 6.5 a few days ago, I’ve had issues with x11 windows running through xwayland. Any window that should start in fullscreen instead starts in a fullscreen window.
Additionally, any window that has its own titlebar and frame (noBorder: true in kwin debug console) can’t be moved around by dragging its titlebar. This affects apps like steam and vscode, so I’m surprised that I haven’t found anyone else experiencing the same issue.
After a solid afternoon of testing, I managed to fix it by updating my bios. No other settings were changed. I have no idea why or how a bios update would fix an issue like this, but if anyone else is facing this issue, give that a try I guess. I’ve got an MSI B650M-A WIFI motherboard, and it was running mid 2024 firmware (August iirc). Updated it to the latest and suddenly plasma is behaving again.