Epicyon could be an interesting app for the freedombox
https://epicyon.net/
Epicyon is an AGPL licensed ActivityPub protocol compliant federated social network server suitable for hosting a small number of accounts on low power systems requiring minimal maintenance, such as single board computers. It’s the ActivityPub equivalent of an email server, storing posts as human readable JSON on file, rather than in a database. It also uses only a small amount of RAM.
Uhh, that looks actually awesome!
I was for a long time looking for a way to host e.g. mastodon or pleroma myself. But all these seemed quite hungry as far as ressources are concerned.
I had a diaspora pod some years ago which worked well on a bananapi despite being based on ruby and tons of javascript iirc. I hoped for diaspy to come but it didn’t really.
Since I hopped onto the fediverse train and feel well there, Epicyon looks quite interesting. I might give it a try.
An important feature for me in mastodon are content warnings. That doesn’t seem to be planned as far as I could see in the roadmap. But as it’s python and HTML+CSS … maybe that could be project for myself 
Or another server — Tavern. This is where you can see Fediverse software: https://fediverse.party/en/miscellaneous