Re-assessing my criticism, I think I’m mostly complaining that I can’t figure out what software it’s running. But I guess the target customers don’t care, since it’s an implementation detail. I’ve only ever heard “oxide” in the past in reference to the OS they were (are?) developing, which a web search says is called “hubris”, so when I see an article like OP I’m wondering “are they running k8s on top of hubris? Wow!” But I’m imagining that’s very much not the case.
In the comments in this very section an oxide employee mentions they’re using Illumos, but I don’t see that anywhere on their website either.
But you’re probably right in that the target customer doesn’t give a shit what OS it runs, so long as they can get instances deployed (although I would question why, if you’re going to run k8s anyway, you don’t just run it on bare metal and skip the hypervisor, but that’s my bias showing up as someone who writes bare metal controller software.)