Note by @fastfinge

@IceWolf @foxbutt No, all you have to do is join a relay server. Then it will send you every post from every other server that also joined that relay server. Almost no relay servers currently require approval to join. Also, because of how threading works, once you become aware of a user (perhaps because they boosted you or whatever), most fediverse implementations will happily let you "backfill": IE allow your server to download every public post of that user so you can view it locally.