Forget gaming motherboards and go for motherboards designed for mining crypto only, they have more than 10 pcie slots for GPU like these two motherboards

1. https://app.alibaba.com/dynamiclink?touchId=1600323725134&type=product&schema=enalibaba%3A%2F%2Fdetail%3Fid%3D1600323725134%26ck%3Dshare_detail&ck=share_detail&shareScene=buyer

2. https://app.alibaba.com/dynamiclink?touchId=1600225240009&type=product&schema=enalibaba%3A%2F%2Fdetail%3Fid%3D1600225240009%26ck%3Dshare_detail&ck=share_detail&shareScene=buyer