--- Comment #28 from Adam Reichold firstname.lastname@example.org --- (In reply to Adam Reichold from comment #27)
At this point, I suspect something SUSE specific being the root cause here: While downgrading the firmware package did help and upgrading to kernel-firmware-20201005-337.1.noarch.rpm from https://build.opensuse.org/package/show/home:tiwai:branches:Kernel:HEAD/ kernel-firmware did also work, just using the plain upstream amdgpu folder from https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git and dumping it into /lib/firmware/updates works as well. (I used firmware_class.dyndbg=+p to check that the update files I fetched directly via Git are loaded).
I am sorry for spamming this bug report, really. But this is getting weirder still: I have no revert to a clean Tumbleweed 20201011-722.1 and everything still works. So booting into the old firmware once seems to restore the system until something unknown happens that breaks the new firmware?!