Sorry for double posting but for the people hitting the issue, please update to the already available 5.12.7. It fixed the issue for me and most other people.
I see also even newer builds but I haven't tried them yet.
With 5.12.6 boot freezed after switch root in boot log. Now it seems to be working. I'm writing with
$ uname -a Linux koTak 5.12.7-300.fc34.x86_64 #1 SMP Wed May 26 12:58:58 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux