I would buy one of Raptor's Blackbird POWER9 systems
[1] if I had the money (they are rather expensive), the firmware for the motherboard is open & auditable, which is nice.
That all goes out of the window once you install a hard drive of course but there's not much we can do about that.
Related:
https://www.talospace.com/2019/06/a-...blackbird.html