After having installed version 5.14.21-150500.55.86 of the kernel release
candidate for SLE 15 SP5 / openSUSE 15.5 on my desktop, the system hangs in
early boot with no video signal. 

When booting with loglevel=7 and drm.debug=0x1e I see that there are apparently
some errors in drm, but they are only displayed for a very short time (< 1 sec)
and then the signal to the display is cut off.

The GPU is a discrete AMD Radeon RX 7800 XT.

What did work:

a) booting with nomodeset
b) creating an update directory in /lib/modules/ for the new kernel and putting
there the amdgpu.ko.zst from the previous kernel, rebuilding the initrd and
booting (see https://bugzilla.suse.com/show_bug.cgi?id=1215802#c11)

This looks like an re-incarnation of
https://bugzilla.suse.com/show_bug.cgi?id=1215802 reported 14 month ago, but
maybe with different root problems.

Currently, I am trying to get a legible video of the booting.