These seem to solve the ‘host your own cloud’ problem, but are still standard server blades requiring a ton of surrounding hardware and maintenance. Oxide is entirely integrated.

"A ton of surrounding hardware" is vague, generally speaking it's bog standard network switches that are needed.

Oxide is entirely integrated with their own custom (though based on OSS?) networking via Tofino based switches and software. Could be good, but a lot of subtle bugs can occur at this layer. It's a risk.

VxRail's the market leader? Last I touched it, it was a mountain of integration faults and vendors pointing fingers at each other. Maybe it's easier in larger or more traditional environments, but I'd be apprehensive of hyperconvered if VxRail's the best available

Evo:RAIL from VMware had those issues, but Dell VxRail has been relatively smooth at scale IME.