I believe the general consensus is 8 cards with Asus z270-p and 9 cards with the z270-a. I recommend using linux distros for more than 8 cards. There are btc specific b250,b350, h81 and h110 mobos, but the prices are heavily inflated if they are not sold out.
Agree as it appears Windows has a limitation of 8 GPU's.
you mean linux can have more the 8 same gpu? this is good to know. How about mix gpu? amd nivida?