Another update here: I remember now what my original problem was with Qlustar after installation: it wouldn't boot. No matter what combination of BIOS tweaks I tried, I got "no bootable disk detected" from my system. Just as a lark, I tried booting from the YUMI key I used to install Qlustar this go-around and told it "boot from the first hard disk," which is actually the default option. Worked like a charm. What this means is that I can only boot the system with this YUMI USB inserted. I tried having it reinstall grub on the SSD. Nope. Still only boots with the YUMI key as a "first stage."
So, Roland and Jeremy -- something Qlustar does with its bootloader, I think, is incompatible with something weird in the HP (not HPE) BIOSes. It isn't just HP: I got the same error trying to boot the Qlustar installer from my OneMix 3S laptop, which has a pretty minimal Aptio BIOS.
Anyway, another datapoint for us to mull over. I will start another thread about my latest round of Qlustar questions ;)