Anyone got the vendor reset plugin working with RC4 yet? It stopped working on RC3 for me. Upgraded to RC4 today and still facing the same issue. I get the same "Unknown PCI Header Type '127' for device" error as @dhstsw if I try to start up a VM after powering it of. Doing a reboot just makes it stuck on the Tiano Core splash screen.
Ich777's kernel builder fixed it for me. I have an RX 5700XT. Let the container do its thing, then simply copy the output to /boot and reboot. I can reboot my VM as much as I want now.