If you can imagine an open source project that was a mix of self-hosted Twitter and P2P torrenting, that's Laconica. Still one of my favorite projects, and could easily be updated for 2019/2020.

I've been using flock for the last 2 months or so. I used to have a ff install loaded up with extensions I never used, but I've found flock to work fine for most of what I do.

I don't miss FF at all, I uninstalled it a few weeks ago. Flock is definitely worth checking out, especially if you use del.icio.us or (to a lesser degree IMHO) Flickr. (Flock uses delicious for its bookmark system, it doesn't have browser-held bookmarks...very nice for mutiple machines (home/work, etc.)