There is a new lemmy instance at startrek.website where people from /r/daystrominstitute and /r/risa are migrating. The communities currently there are:
I'm posting this here on !startrek@lemmy.ml because, with >500 subscribers, it is/was the largest startrek community on lemmy by subscriber count prior to the presently ongoing influx of new users from rexxit.
You can hopefully click the relative links above to access these communities through whatever instance you're reading this on; if you get a 404 then you'll need to go to startrek.website and copypaste the link to each community into the search box on your home instance to cause it to federate them.
Sadly startrek.website is already blocking federation with lemmygrad, home of what has historically been imo the best (and largest by number of posts) trek-related lemmy community !startrek@lemmygrad.ml (here is an absolute link, so people reading this from instances that block lemmygrad can see it). I hope the startrek.website admins will reconsider this block!
edit: here are some other lemmy-or-federated startrek communities from the comments here, and elsewhere: