Comment # 14 on bug 1172924 from Freek de Kruijf

(In reply to Franck Bui from comment #13)
> Can you try to pass "nomodeset" to the kernel command line before booting
> your system ?
> 
> Not sure if that will help but at least that should make the following udev
> rule (in /usr/lib/udev/rules.d/71-seat.rules) to be applied to the frame
> buffer and hence add the missing tag:
> 
> > # Allow efifb / uvesafb to be a master if KMS is disabled
> > SUBSYSTEM=="graphics", KERNEL=="fb[0-9]", IMPORT{cmdline}="nomodeset", TAG+="master-of-seat"

This did indeed help. Now I can start a Plasma session.

> That said I think it would better to report this issue directly to upstream
> as it isn't specific to SUSE and I'm not sure how this should be properly
> fixed...

Should I do this? If yes, what is the upstream bug report location?