Epic, which most large hospital systems seem to run, has a Linux version but I’ve never seen it in the wild. Every healthcare worker I’ve met loathes Epic — I asked around about it because a doctor and nurse complained about it to me randomly because I’m a developer. I live near some hospitals so I often chit chat with healthcare workers who are neighbors or at bars or whatever. I wouldn’t consider people commiserating about work at a bar to be a representative sample but it seems like complaining about Epic is a thing.
I also don’t know for sure if this is 100% true but healthcare IT people have told me never to work for a hospital because HIPAA violations (like a data breach) can make the IT guy liable for the violations. I looked it up once and it seems like it’s more C-suite people who are actually held liable. (but more likely a CTO or CEO) can be held liable. But the threat is there and having another company to blame is a big reason some institutions use Windows. No one saves you if a Linux vulnerability exposes patient data.
Again, my source is barroom banter and not lived experience. Hopefully, someone with direct knowledge can correct me where I’m wrong.