Postmill looks really good but I don’t see any mention of federation on its homepage.
Checking their Gitlab description it looks like you are right. The OP mentioned Reddit in the post title though, and Reddit is “still” not federated ;-) Using https://fediverse.party I found these as well :
deleted by creator
There are certainly other social news sites, but Lemmy and Reddit are by far the most alike. Most critically, they both are focused around segmenting into user-created and user-moderated sub-communities. That’s as opposed to sites like Hacker News that are also social news sites, but only have a single feed or Slashdot where the topics are chosen by site admins.
Digging via https://alternativeto.net/software/reddit/?license=opensource&p=1 Here’s some of the 55 results :
saidit dreadit theyre both kinda dumpy
