Good idea, but I have no keyboard or mouse access immediately after I am able to log in on the problem cMPMaybe you need to remove and reapply post-install root patches because the Nvidia card needed patches which cause problems for the AMD drivers now?
However!
I do have a second macPro 5,1 with the same AMD Radeon Sapphire RX580 Graphics Card, so I'll attempt to do that with the drives on the macPro 4,1-5,1, assuming the post-install root patches are applied to the SSD drive with the OS.
I'll report back soon in case this helps anyone else who ends up with a similar problem.