Off the top of my head (should work in kbin, not 100% sure though), if you search for that community (battlemaps@lemmy.world) in the community browser and possibly wait a while, you should be able to subscribe to it.
It might take a few minutes for the server to look the community up if it hasn't already been subscribed to by other people, but should work!
Thanks for the assistance everybody, i'm now successfully subscribed to battlemaps.
The Fedia.IO copy of it is showing no threads, but I assume federation isn't a back porting process and i'll get new posts over time. If anything, there's always the original instance if I want to browse it's history.
Thank you for the help.
That's correct - kbin doesn't tend to drag in old posts, however Lemmy does appear to do this.
I see, thank you for the clarification. Maybe thats something that'll change in the future, but only time will tell.