Shameless self-promotion: We’re trying to keep an overview of all things social media that have been recognised as important to various parts of the Google+ Communities on this wiki: https://social.antefriguserat.de/index.php/Main_Page
The result may actually become a template that could be applied to a new platform built on Solid. If there are folks here interested in doing that, talk to me! 
(“We” in this context are Just your average space alien cats and other unsavory types)