Can't connect two SATA drives to HP OmniDesk Slim Desktop S03-0000i

I have an Omnidesk Slim (running Debian) with two SATA ports on the motherboard. I got the necessary adapter cables and plugged two HDDs in. Both drives work and both SATA ports work (tested separately), but the drives do not work if they're plugged in together. I checked UEFI for some way to turn off RAID thinking that was the issue, but can't find anything. Running UEFI version F.08, which is the latest I can get through fwupd.

reddit.com
u/Eldus_Miku — 2 months ago

[Motherboard] ASUS B760M-AYW WIFI D4 II PCIe 5.0, 2x M.2 slots, DDR4, Realtek 2.5Gb Ethernet, Wi-Fi 6 - $89.99 ($99.99 - $10 off with code SSF72776)

newegg.com
u/Eldus_Miku — 2 months ago