Hetzner is buying ASUS consumer AM5 motherboards, but with the whole CPU + memory block rotated so that the memory sticks are horizontal instead of vertical for better airflow:
They have lots of different boards, among others ASRock. Even within the same range of models you can buy, for instance AX52 you can get different manufacturers. It's not really transparent to the customers when they order.
https://www.youtube.com/watch?v=V2P8mjWRqpk