XMPP is the closest social network in line with Richard Stallman’s vision of the internet. This instant message protocol, allows for you to easily host your own server, it’s fast and efficient, and has lots of different open source clients to choose from. Additionally, by making it extensible, it allows for anyone to build upon it to get their own desired features. This article goes over some of the basics of XMPP: https://simplifiedprivacy.com/xmpp-decentralized-signal-get-your-own-social-network/
Note: There are no affiliate links or sales text in this educational article discussing open source. Let’s discuss the technology and not attack the author.
There’s no mention though in the linked article that Richard actually thinks this? Both XMPP and Nostr are extensible. Nostr saw accounts linked to a server as weakness, and therefore went with many relays (any of which can be used).
But as also mentioned, Richard is actually very active on Mastodon today. ActivityPub is not the best protocol around, but it is now a W3C standard and seems to have more popular uptake than both XMPP and Nostr (Nostr having the excuse that it is very new still).
BTW I’m active daily on XMPP, Nostr, Mastodon, IRC, and many more, so have no particular stake in any one.