back in course and working now. I upgraded to Leap 15.6 with only the essential repos activated. Kernel 6.8 something was still installed afterwards, removed it. Only leaving the 6.4 of the repos. Nvidia drivers were built and are loaded at boot. but I got blank (black) screen(s) - couldn't switch between consoles, when the nvidia drivers were loaded in the initrd. I finally got it to work when booting with "nomodeset" so got finally 3 working screens (nvidia modules loaded) and I started the display-manager.service. The initialization and login and reinitialization took ages (more than 5 minutes). But it works. Thank you all again for your help. Most importantly I learned, not to do a distribution upgrade with all repos activated. But thought, that "unmaintained" packages or those installed with a higher version than in the repos would be uninstalled or downgraded respectively - but that doesn't seem to happen :-/ Regards Paul