Comment # 27 on bug 1177428 from Christian Hartmann

I might have a similar issue... After doing a zypper dup today I cannot boot my
computer.

In the rescue system I was able to see some errors in journalctl regarding
amdgpu.

(In reply to Takashi Iwai from comment #23)
> BTW you need to update only amdgpu firmware:
> % zypper in --oldpackage --force
> http://download.opensuse.org/history/20201007/tumbleweed/repo/oss/noarch/
> kernel-firmware-amdgpu-20200916-1.1.noarch.rpm

Downgrading the kernel-firmware-amdgpu package fixed the issue.