It's worth mentioning that the more principled alternative is GNU Social: https://gnu.io/
I'm sort of tempted to try writing a UUCP- or NNTP-based GNU Social clone now.
UUCP or NNTP are really interesting suggestions. They are protocols of the old net that seemed to scale very well and long ago solved many of the kinds of issues I'd expect to see with something like a federated Twitter clone. Maybe I'm overestimating the scale of newsgroups during their heyday?
https://www.microsoft.com/en-us/research/publication/picturi...