[xigoi]

E-mail providers allow you to use a custom domain, so if the one you’re using suddenly goes away, you can just point your DNS records at the new one and that’s it. If the ActivityPub instance you’re using suddenly goes away, you can say goodbye to your account.

[__d]

Unless I'm missing something, that's exactly the same.

If you're using someone else's email domain (like, eg. gmail.com), you cannot migrate to another provider. If you use your own domain, you can change who is hosting it.

Like email, there are plenty of Mastodon hosting companies. You can use your own domain, and migrate between them at will. If you use eg. mastodon.social, you can even migrate in most circumstances (but not if the instance vanishes).

[xigoi]

The difference is that you cannot use someone else’s instance with your own domain. You have to get your own instance, which is much more expensive and creates a lot of duplication.

[__d]

It would be nice to have a server that supported arbitrary domains. Perhaps https://jointakahe.org/ would suit?

OTOH, eg. (not an advertisement, just the first search result) masto.host offers managed Mastodon hosting for $6/month, which is on par with eg. Fastmail or Proton's base non-free plan.