> Didn't Munich do this like 20 years ago and it was a complete failure?

Yes, but the failure was basically manufactured. You cannot keep every process as it was before and just install Linux/libre office, yet that is what they did.

Their current processes are optimized for windows to a degree that usage of the Microsoft office suite is part of the training they undergo.

Switching at this point would be a multi-year process that cannot be rushed. Each task needs to be evaluated separately and a new solution has to be tested and likely engineered from the ground up.