Ooh, just followed my first lemmy community from Mastodon. Seems I just have to replace the "!" with "@" when I search for them. They seem to show up as a "Group" here. Nice!
Given Trek fandom are often the first colonizers of online spaces in internet history (eg newsgroups) losing major Star Trek communities is big L for Reddit.
EDIT: Not permamently locked subreddits, got that wrong I think!