Comment # 1 on bug 1210146 from Manfred Hollstein

I just tried booting the (recovery mode) variant of the 6.2.9-1-default kernel
and, guess what, it booted without any issues. When the retbleed stuff became
available I then added "mitigations=auto spectre_v2=retpoline retbleed=stuff"
to my /etc/default/grub and forgot about it... FWIW, I didn't do that on Leap
15.4 which is why the kernel there booted successfully.

I now removed these boot parameters on all my systems and everything works
again. BUT, this means that the "retbleed stuff" is buggy in 6.2.9!