[severine]

"So, a Mastodon alternative has to be selfhosted by default, and infinitely easy to set up for selfhost."

You might be interested in Holos: "Holos turns your phone or computer into a full ActivityPub server. No big-tech hosting, no middleman reading your posts. A relay keeps your identity online 24/7 while your device stays in your pocket."

https://holos.social/

[numpad0]

That's close to what I had in mind, but relay architecture is not enough; people will "abuse" the relays, and relay server operators will find it uncomfortable. Relays shouldn't be hosting content at all.