I found this thread and thought Plasma was crashing for me too because all I saw was a black screen with a cursor. Turns out I could launch apps with Krunner (alt>space) and all the apps behaved normally. I could also play a video file with VLC. I just don’t have a desktop with the panel. I have all of the latest updates and I’m using nvidia driver 510.54. Anyone else getting this or know of a bug that’s already been reported?
https://forums.opensuse.org/showthread.php/566620-Plasma-Krashes-when-i-boot-to-Wayland