I've got an R230 with a SATA SSD connected to the internal USB port using a  USB to SATA adapter. I've installed TrueNAS SCALE to this SSD but I am unable to boot off of the SSD. If I go into the UEFI One-shot menu I see TrueNAS' bootloader (labelled as debian) listed but I'm unable to choose it as it's greyed out.

I have updated all the firmware in the R230.