Employers requiring that I use Windows on a computer they provide has been a thing, once or twice. It's their computer, so no argument from me.

Nowadays that would be pretty weird thing to do though. I mean, I'll gladly do it if you're paying me by the hour, I guess.

I'm actually looking at rolling Linux exclusively at some clients. The employees are working through a web app. All the ads, interruptions, and poorly tested updates in Windows waste time, but not enough to be a problem worth solving on their own. It's managing software licenses that's just too much of a pain when we need to suddenly bring on more staff (it's a small business so no dedicated IT department). Easier to just have a standard Linux image that I show up and spam onto a dozen hard drives. I'm available for maintenance, but it's never actually been required.