https://en.wikipedia.org/wiki/LiMux
"February 2017 - Politicians discuss proposals to replace the Linux-based OS used across the council with a Windows 10-based client.[42]"
https://www.heise.de/newsticker/meldung/Muenchner-IT-Leiter-...
In short, there are no technical problems whatsoever. It's just a strong lobbying...