I performed a fresh install of openSuSE 15.5 in a VM running under VMWare Workstation (host is openSuSE 15.4). When I log in under KDE with either Wayland or X11 and let the login sit for about 15 minutes, the screen goes completely blank, and does not respond to either key presses or mouse movements. I have tried flipping between full screen and back in hopes that would trigger responses, but to no avail. Now if I select XFCE as my desktop, I don’t experience the issue at all so guessing it is something with KDE. Any suggestions on how to proceed to figure this issue out because I am not sure how to proceed.
It is possible that your system is (attempted to be) suspended. I had similar issue using QEMU and had to turn off suspend on inactivity everywhere.
I believe you found the solution. I had disabled the screensaver, but apparently I hadn’t thought of the suspend. Many Thanks!