Check out Talos II motherboard. It's a workstation-class motherboard with dual POWER9 CPUs for $2750. It's a good price for workstation computer IMO. They claim that all their firmware is open source. Specifications are quite modern. The only problem is (kind of) exotic architecture, but many people would be able to use it with open source software.
I was scanning thought he comments to see if somebody had already mentioned this and if you hadn't I would have.
I am finding the Talos II an increasingly attractive proposition, even though the prices got a full system are quite staggering by comparison to mainstream hardware.
