Solution/fix found: *Confirmed* Changing the PCI-E gen speed from the default setting of gen1 to auto and/or gen2 in the motherboard bios solves the 20 series install issues on both ASUS B250 and H370 Mining MBs.
Thanks goes to Someone_2 of the Ravencoin Community discord (mining section).
I have the same problem with this board and changing to gen2 does not help me(( I need to run 12 * rtx ASUS TURBO 2080ti GPUs
could you share what else did u changed?