In the top bar there's https://lemmy.ml/communities, where you can find a list of communities based on different kinds of measures, there you can select if you want to see the list of communities you follow, local or across all of the Lemmy instances. Also there's https://lemmy.ml/c/findacommunity where you could ask if X or Y community exists.
I feel like that would be great. While there are community browser options, it would be nice if you could subscribe to the community-community to see new communities as they just start and being able to read someone's intent/mission statement and ask/read questions in that introduction post.