I will say that Mastodon actually does this quite well... they key challenge is lack of US adoption, which means whole US centric interest groups (like AI/LLMs) aren't on it. But if you're in, for instance, German hacker spaces, it's a perfectly passable Twitter alternative with actual working federation.
The challenge to Mastodon isn't adoption, its absense is a symptom of a deeper issue: it's a Very Bad Idea to trust random server operators with both your data and it's sovereignty.
You can take your data to another server only if the original server is up. When the admin forgets to pay the bill and ISP nukes the box and the backups admin said they had don't exist and the coadmin turns out to have no access at all, you lose everything. Ask me how I know.
Self hosting in theory should fix this but it doesn't: it's a resource intensive afterthought because the developers only really care about their Big Instance.
