I have two M.2 NVME drives and one U.2 drive on my ASRock X399M Taichi motherboard. If I run in AHCI I can see all three drives. In fact I was running Windows 10 on a single M.2 drive and had a software mirror setup because I couldn't setup NVME RAID without the U.2 drive disappearing. I saw there was a BIOS update on ASRock's site that said the RAID ROM was updated so I decided to try it out again. The BIOS update didn't change anything and my U.2 drive is missing.
Is this not a supported configuration?