I have been advocating for a while how easy it is to integrate a lightweight XMPP server with fediverse instances. The accounts can be easily linked and the user address is the same.
Here on slrpnk.net for example every member automatically also has an XMPP account.
It runs on any old raspberry pi (any but raspberry pi 1 I believe) in your house, can be used by family and friends as well. Has iOS and Android apps... I have had good experiences with the easy to set up https://snikket.org/ XMPP server.
"Hey bro! Here's some 20 year old program! We should totally reinvent it today! It's not like anyone has been working on this exact thing for the last 20 years!". Wtf is with the younger generations obsession with "retro tech"?!? "Look bro, I can do the same thing we can do now, but slower and worse!"
Also Matrix. If you're gonna suggest something, maybe make sure it doesn't already exist.
All these people "rediscovering" old tech like we didn't abandon it for a reason. No, I don't want to build a PC out of old Commodore 64s that barely works and needs to be coded in assembly when I can literally get a mini PC that's 100x more powerful for $120.