As exemplified by a major project recently started by the French government:

https://www.rfi.fr/en/france/20260417-france-to-remove-windo...

https://www.techradar.com/computing/windows/france-has-ditch...

I'd guess the hurdles are always more structural and organizational - as even with Microsoft stack itself. See for instance the Limux/Munic story: https://lwn.net/Articles/737818/