I am running 6.12.1 for some days and had trouble getting my Palit GTX 1060 3GB to passthrough.
Eventually today I tried the it WITHOUT a vBIOS. Not modified, not unmodified. It just works!
With vBIOS (modified or not) it wouldn't start the VM. It would hang with 100% on one Hyperthread.
I think they added nvidia support? For some cards at least?
I don't know. But i am Happy that it works! I was just one or two steps away from going back to 9.6.2