Are you using hardware with a dedicated gpu and an igpu?
If you have both, you can just blacklist the pci of the gpu that is not working with rd.qubes.hide_pci=xx:xx.x in grub.
But if neither of the gpus work with qubes, you are out of luck.
You might want to install the latest qubes release candidate with kernel latest and see if that helps with the hidden pci.
Another thing you might want to try is updating your bios before you try to reinstall qubes.