Thank you very much for providing this guide.
Since fedora templates got updated, I tried to adapt your guide to the latest templates. (As of now this is fedora-43 , version 0:4.3.0-202601041226 ). Unfortunately, I probably ran into an error that I believe is the same error as Antar and redheart have reported.
It seems to be that just a sole sudo dnf remove openh264 triggers a removal of 700+ other packages, including qubes-specific administration packages and others that seem vital to me on first glance. During this transaction the command aborts.
Since I got so surprised about this behavior, wondered what happened - and doubt that it works as intended, I outsourced the openh264 removal into a dedicated thread: