ActionRetro, the youtuber who does a lot of retro computing videos
recently created his own Mastodon server catered around retro
computing.
https://bitbang.social/
I know there are a lot of SDFers that would be interested in the
content over there. It's also a pretty good way to actually test
federation on the SDF mastodon instance. I've already followed a
few people on bitbang. It is kind of clunky but it does work.