I recall several European nations switching government systems over to Linux only to have Microsoft worm their way back in a few years later. Let's hope it's permanent this time.
This has never happened at the nation state level in Europe.
I don't think it's a good idea anyway to switch every client over, but it would be nice if governments would consider Linux for servers more. The default assumption of new machine = new windows licence is very wasteful.
Governments are actually an ideal place to switch over the clients, because they're large enough to deal with it.
If you're a small business and your files are in Microsoft formats and none of the conversion utilities are very good you're in trouble. If you're a government with hundreds of IT staff, you can improve the conversion utilities. You can make "runs on Linux" a requirement for software you buy and be large enough that vendors will port their software to Linux in order to get your business.
That is why Microsoft is so afraid of governments doing this. Because once the conversion utility is improved, it's improved for everyone. Once the vendor takes the time to do a Linux port, it exists for everyone. Which makes it cheaper for other entities to switch to Linux, which causes even more progress in reducing the friction to switching for everyone else.
Ideally yes but in reality no. Governments are the ultimate "enterprise" IT environment. Highly ossified and completely dependant on outside suppliers. On top of that procurement processes take a while. So there's a whole ecosystem that's slow to change that has all been built with the assumption that it will be ran on Windows server. Any changeover process would take so long it's unlikely to survive every political change of guard during that time.
That's not even mentioning things like the extreme reliance on Microsoft AD.
This is why you do what Munich did. Step one, before you install your first Linux machine in production, require all your software to run on both systems. That also trains the users to use LibreOffice and Firefox and so on, even though they're still using Windows, and you can do one application at a time over however long it takes. No new software is permitted that won't run on Linux, even while you're still on Windows, and any existing software gets phased out.
Step two, you change out the underlying OS and people barely notice because all the applications are the same.
I think basically Linux didn't work that well for them more than "MS worming their way back in". It sounded pretty pragmatic in the case of Munich from what I read.
It looks like you've read only part of the story. The part I read was about Microsoft putting a lot of effort/money, including lobbying, into making Munich switch away from Linux, and now, as the sibling comments point out, Munich is switching back to Linux.
I don't think it's a good idea anyway to switch every client over, but it would be nice if governments would consider Linux for servers more. The default assumption of new machine = new windows licence is very wasteful.