Here are some resources on Open Source Social Media.

Wikipedia / short summaries: Fediverse, Diaspora, Friendica, GNUsocial, Mastodon, PeerTube, Pixelfed, Pleroma, Pump.Io. General overview of alternatives at http://switching.social/

Peertube Introductory Video

Mastodon Introductory Video

Fediverse Intro
Fediverse.Party

General technical overview: A quick guide to The Free Network
https://medium.com/we-distribute/a-quick-guide-to-the-free-network-c069309f334

“#Friendica vs #Hubzilla vs #Mastodon”
https://blog.windfluechter.net/content/blog/2018/08/25/1747-friendica-vs-hubzilla-vs-mastodon

Here is a good introduction to twitter replacement Mastodon:
https://lifehacker.com/a-beginner-s-guide-to-mastodon-1828503235

MORE on Mastodon: http://www.jweeks.net/mastodon-articles-tips-and-tricks

Friendica Case study
Friendica – the secure social network with data sovereignty

https://greennetproject.org/en/2018/03/19/friendica-das-sichere-soziale-netzwerk-mit-datenhoheit/

“Nomadic Identity” – take your posts where you like
Nomadic identity, brought to you by Hubzilla
https://medium.com/@tamanning/nomadic-identity-brought-to-you-by-hubzilla-67eadce13c3b

Hubzilla:
The Do-Everything System: An in-depth review of Hubzilla 3.0. https://medium.com/we-distribute/the-do-everything-system-an-in-depth-review-of-hubzilla-3-0-692204177d4e

Jami: Free Open Source Skype Alternative https://diasp.org/posts/fcc401a0e69701364994001c4202e28a