H81-BTC 6 GPU Charger Mining Motherboard With 6 PCI Express Riser Card USB 3.0 PCI-E 16X Express Extender Riser 1X To 16x - Price history & Review | AliExpress Seller - Taotuo
The ASUS H370 Mining Master connects 20 GPUs to one motherboard with PCIe over USB - Edge Up
I use a ASUS Prime Z390-P Motherboard for 6 GPU. Currently i can't use more than 4 gpu at the same time. Maybe i have to change some settig in the Bios.