The contents of the files below would help in diagnosis.
/etc/modprobe.d/vfio_pci.conf
/etc/modprobe.d/amdgpu.conf
/etc/modules
/etc/initramfs-tools/modules
the line- GRUB_CMDLINE_LINUX_DEFAULT= in /etc/default/grub
Also, have you updated your initramfs for all kernels and rebooted? Anytime you do something with modules/modprobe config you should update initramfs.
I had to manually add the vfio and vfio-pci drivers to my initrd then manually rebuild my initrd but I have set this up in the last few days and it worked fine.
Um, as the pci id’s look correct, it could be that radeon still is loading before vfio.
Aren’t radeon and amdgpu different drivers/modules? If so, your gpu is using Radeon and you have amdgpu as your softdep after vfio. So maybe also softdep Radeon and update initramfs and reboot? All of my newer cards are Nvidia(mining… sigh) so I don’t know the specifics of amd drivers.
If still does not work you could try blacklisting radeon/amdgpu if your host gpu is using a different driver(ie a nvidia or intel chip).