After commit 0bc3126c9cfa0b8c761483215c25382f831a7c6f in linux-firmware my system stopped booting (due to being unable to mount root fs). The bug isn’t occurring all the time even with this commit, but I’ve still successfully tracked it down to this specific commit. Now I’m not sure where I can report it, as I could find info about maintainers of certain Linux subsystems, but not of linux-firmware or its constituent parts (like amd-ucode).

Edit: I’ve sent it to the person who authored the commit for the time being