So in short I decided to forego my usual options and to check out OMV. I installed OMV on my HP T620 Plus which has a m.2 SATA SSD. I'd booted the install USB in UEFI mode, FWIW. The installation looked okay, though on the first pass it told me one of the partitions was locked and it would not repartition the entire drive as directed.
I rebooted and went through it again with no obvious issues but when it is complete and it tells me to remove the media I get a Boot Device Not Found message. Usually this has been a boot sequence thing in the worst case (I have a couple of these T620s I've loaded this way many times), but it just isn't working here. Any ideas? I've checked the BIOS and it all looks fine.