Lemmy is entirely federated with mastodon now. there are many issues still but you can look up a lemmy community by @communityname@lemmyinstance.domain from mastodon and follow it there and then you will recieve all posts from that community in your home feed. if you want to reply to a spesific lemmy post from mastodon (broken on instances running 0.18 but working on earlier versions) you can copy the link from the little rainbow fediverse icon on the top of the post and search it from mastodon, and it will load internally and then you can respond from there.
Glad you started this repo, I have been continuing to update my chart with instances I have found, but so far mostly just focusing on the intermix of fediverse software under the same control. I see you have been focusing just on cooperatively run galaxies, which I think is definitely the direction we need to take in the long run, but there are seemingly very few.
you can look at the account on this side https://lemmy.ml/u/threadcount@botsin.space but I don't think you can even "follow" users on lemmy, but that is a good question and I am still getting my grip of how lemmy works, I never really used reddit so I don't know what the assumptions are
