For server hardware form scratch build, I'd expect just as little support issues. I know what platform I'm building towards so I'd select hardware components that are supported in the first place.

Dell, I'd expect there rack boxes to work just fine also being that they offer a "no OS installed" option for cross platform and support Ubuntu.

The only place I see it being a real issue is if your forced to use specific existing and obscure hardware. For a server box or workststion, you don't need any obscure hardware unless it's a specialized need like a CAD workstation.

So, the question comes around full circle again. What server hardware still has support issues and why would one be forced to choose those unsupported components?

(I personally prefer to speak the only language business understands and vote with my wallet; no support for multiple platforms, no money for them.)