On currently R6E firmware version - 1301, this motherboard didn`t support 905p u.2. I dont know about 905p Add-In Card, but u.2 dodn`t recognized form BIOS on this motherboard.
Im tested on two Optane 905p disks.
All two disks, is perfectly recognized on other MB, as from Asus and also from other MB brands. And avaiable from bios boot menu right away.
On R6E im try:
1. Connect via U.2 to SFF 8643 from disk box.
2. Connect via u.2 to PCIE adapter
3. Connect via u.2 to m.2 adapter
In all 3 tests - disks not avaiable from R6E BIOS and also from win 10 intsallator.
Im contact to Intel and Ausus support, for resolve this problem. But currently - i do not recomend for purchase this Mb-Disk combo.
This is very sad situation TOP MB and TOP SSD from very famous brands, with so lot of marketing. And.... Didnt work.