Make posts to them…
Lots of people browse by /all and /new because of lack of content.
Which means it’s relatively easy to get a sub to catch on
But you need to actually make posts so people see them. Try to space it out tho, 15 posts in 15 minutes will just get people to block it due to spam. A couple spaced out thru a day tho will start getting more interaction, go for quality not quantity and hope eventually other users start submitting stuff for the quantity part.
If you build it, they will come. (i.e. just keep posting)
Lemmy is still small enough that even the most obscure communities will show up on the All feed, which it seems is how a lot of people browse. If you post to your small community, especially during non peak hours, some people will see it.
Post to
Consider collaboration with similar communities. !fedigrow@lemm.ee is a good place for that
Fedigrow community is one option.
Probably just activity? I mod a sub thats practically dead. I mean I’ll post again soon. But its pretty much dead.