Essentially as long as your instance isn’t actively defederated from a given instance, you can typically join your instances “mirror” of that community.
Say you wanted to join cats on sh.itjust.works… you can open your instances search and paste !cats@sh.itjust.works into your search
Because currently lemmy doesn’t substitute links to rewrite them from your own community.
Eg. !cats@sh.itjust.works would refer to https://lemmy.one/c/cats@sh.itjust.works From your instance. If people don’t link correctly though it’ll direct to https://sh.itjust.works/c/cats which you wouldn’t be able to join
Essentially as long as your instance isn’t actively defederated from a given instance, you can typically join your instances “mirror” of that community.
Say you wanted to join cats on sh.itjust.works… you can open your instances search and paste !cats@sh.itjust.works into your search