UPDATE - Solution
It looks like AGESA AMD BIOS version 220.127.116.11 Patch B (1004 B) fixes the Nvidia pass-through D3 errors for folks with x470 and x370 Ryzen AMD motherboards. This patch was introduced in late November 2019 to AMD motherboards. Mobos confirmed working after updating to this BIOS version:
* Asus Prime X470 Pro + 3900x
* MSI B450 Gaming AC
* MSI x470 Gaming M7 AC + 2700x
* X370 Taichi + ryzen 3900x
* Gigabyte AX-370
* Asus x470-F with 2700x and 39
After i added 2nd GPU card - needed to do some testing...all was good. Then removed it , kept only one and the same issue started again and FREEEZEs.
Read through your notes, some custom patch has to be applied (for version 6.8.3). I was already on 6.9.1b22 so not able to revert 2version back.
Anyway not really sure how i was able to run it before without any patch, but i assume this is the way:
I wasnt able to start VM module, soon as i wanted it freeze with error b