The issue was the BIOS graphics settings I believe. I did a few things at the same time though, so I can't be sure what actually solved the problem.
Here's what I did...
Flashed BIOS from 2.30 to 2.50
Changed BIOS Primary Graphics Adapter setting to Onboard (default after BIOS reset was PCIE)
Removed all boot priority options besides UEFI on unRaid flash drive
Set CSM Enabled
Boot Option Filter changed to UEFI and Legacy
Mounted unRaid flash drive on a different computer and renamed EFI- directory to EFI
I've rebooted the syste