Did you get anywhere with this?
I've tried 3 different cards now all with exactly the same result (as described in the first post)
R5 230
GT 710
GTX 1070
I had a GT 760 I was passing through without any trouble but "things" started acting up. The eventual solution was to pull the 760 but not before I tried a system BIOS update. It sounds like that was a mistake and I cant flash back
Currently running the 710 as system and passing the 230
If I dont try and pass through a rom the screen never lights up, vfio: Unable to power on device, stuck in D3 appears in the log but the VM eventually does start (I get a steam notification)
If I shut down the VM I cannot restart it
Turning off the VM service then restarting it give a libvert failed to start error
After any attempt to start a VM the server will not restart/reboot and I have to hit the reset button or power cycle
1700x on a Prime x370-pro