I just did
zypper dup
a couple of minutes ago. Admittedly I didn't have a close look on the output, but zypper appeared to finish successfully. After a system reboot I cannot get to the Luks password prompt any more.

What I still see is Grub and the kernel loading, and then the screen goes black and that is.
Recovery mode or choosing the previous kernel image does not help.

Maybe someone around with an idea about how and where to start?