I've heard of Robbie! is a user on cybre.space. You can follow them or interact with them if you have an account anywhere in the fediverse.
My friend is planning to spend some time tomorrow researching setting up either a Mastodon or Pleroma server with a #solarpunk bent running on a solar-powered raspberry pi/similar device! I don't know if there's already a solarpunk instance yet or not, but I'd definitely join one.
@Alamantus There is one, https://sunbeam.city/about, but I don't know if it is solar powered, that is a neat idea!
@Alamantus https://sunbeam.city exists