To answer the OP:
ASROCK AB350 Pro 4 - Craps out after 4 cards. Will POST, but Windows won't complete boot. Tried using M.2 adapters and everything, but it didn't work. Maybe in the future with bios updates.
I had no issues getting the AB350 Pro 4 to detect and mine with 6 x GPU's running EthOS.
I could not get past 4 cards
Did you change anything at Bios?
If yes, could you tell us what has changed?
I thank you
Not that I remember, it was quite a while ago that I set the board up though.
It has 5 x GPU's running without issues, and I expect it would do 6 if I had a PSU here to support adding a 6th GPU.