Munich made headlines for deciding to switch to linux in 2003 and decided to go back to windows in 2018.

https://en.wikipedia.org/wiki/LiMux

I still don't understand why major nations don't create or help create national OSes for their own countries/industries. You would think an OS is national security issue at the very least. A municipality isn't going to cut it. It's going to require a major national effort to stave off a monopoly like microsoft.