This is certainly a growing trend which was first started amongst end-users themselves, and slowly we've seen a few news media outlets also following suite. So far, only a very few government agencies have actually followed. Coming to mind are also The Netherlands. What is attractive for many organisations and agencies on Mastodon, is that...
The more important thing: anyone can see their posts now. This is rather crucial for a government institution’s feed and not true on Twitter anymore.
This - Twitter is currently not usable without an account. You can’t see any posts and there’s no way to ensure that your followers will see your posts. Therefore it’s really useless as a communication channel for government information.
They don’t share anything important on there anyway.