I have been using gigabyte fintech B250 for almost 2 years, I used this board for building a 12 GPU rig with 6 Nvidia GPU + 6 AMD GPU. I also used gigabyte H110-D3A (6 PCIE) + PCIE multiplier expansion hub riser card with 9 GPUs connected.
Both motherboards working properly and easy to setup

Nice setting Buddy. I have used several motherboards, even Asus prime z270-a which is too expensive lol, and I think B250 and Giga H110-D3A are my most favorite ones, they are cheap, durable and dedicated for mining.