zulip seems to me like it would be a better solution to me (open source, self hostible, familiar paradigm, etc), but then again, I think _anything_ would be better than teams... so more power to them!
France’s government uses Matrix. Presumably a nice perk to be able to talk to them via federation
Germany (government and armed forces) and NATO also use it.
Germany?? I can’t imagine unless they’re using it to send pictures of signed and stamped printed and scanned letters
Germany doesn't universally use it but its used in germany, for example for healthcare.
I'm not sure if it ended up being used this way, but if I recall correctly, when that was being initially implemented, federation was actually a core feature: different agencies / municipalities / etc could have their own servers and control their own data and accounts, but inter-agency conversations and rooms would be well-supported, along with each agency retaining a copy of the rooms on their own servers.
so Matrix doesn't have self hostable open source options?