I’m honestly surprised more Universities and governments aren’t also hosting their own instances.
Here where I live most universities have their own mail server, dedicated (and open and free) mirrors for popular Linux distros, their own RSS feeds with podcasts and open access to their publications, open source tools replicated, and so on. But most still rely on Instagram and Twitter for public-facing announcements… Why? Imagine having to use tax money to pay for a Twitter blue license.