To add to this, anyone can turn their website into a social network using ActivityPub. For example, if you have a WordPress blog/site then you can use this plugin https://wordpress.org/plugins/activitypub/. This then allows profiles from other networks such as Mastodon to follow, read and comment on your posts or statuses.

I've always found it disturbing how Gargron rarely makes any attempt to disabuse people of the incorrect notion that Mastodon was the start of, and the canonical example of, open and federated social networks.

If anyone deserves that sort of credit, it would arguably be Evan Prodromou and the original identica a decade ago. Though I could wrong, and unaware of anyone prior to him working on this sort of federated and open twitter clone.