Ok so I installed F38 to a LUKS encrypted external portable hard drive and booting into it with the KVM worked as expected. But I didn’t realise that F38 fresh installs kernel 6.2.9 by default which is already working with the KVM. I then did a distribution upgrade from F37 to F38, following Upgrading Fedora to a New Release :: Fedora Docs. The latest kernel 6.4.11 is installed and with the KVM it is still broken. I still didn’t realise 6.2.9 was the default kernel after the fresh install so I thought maybe my previous install was corrupted so I reformatted / and reinstalled a fresh F38. I did because because the external HDD install worked. That is when I realised 6.2.9 is the default after a fresh install and that is why the external HDD install was working, not the upgrade to F38. Oh well, fortunately I have Ansible to reinstall and reconfigure everything automatically plus a separate /home partition so it was no big deal to recover.
I then manually installed 6.2.15 inside of F38 and booted it with the KVM and it works as expected. I then manually installed 6.3.3 inside of F38 and booted it with the KVM and it doesn’t work as expected. I then installed the 6.1 long term support kernel and booted it with the KVM and it worked as expected. There seems to be an issue with my KVM between kernel 6.2.15 and 6.3.3 in both F37 and F38. This is what I will focus on with the AMD bug ticket.