Maybe the Social Web?

Make sure you don’t redirect all users to the same instance. One instance in particular is having too many users (see: https://lemmy.ml/post/1147770 )
People can find a server here: https://join-lemmy.org/instances

I don’t know how Lemmy or Kbin work internally, but I believe merging 2 communities could be similar to a user migrating to another server. Account migration on the Fediverse works by having the old account being setup as a pointer to the new account, effectively merging the old one into the new one. Followers of the old account will automatically follow the new account.

Since Lemmy and Kbin’s communities are, behind the scene, like user accounts boosting messages posted in them, you can see how a community could be marked as “migrating” into the new one.

Another option would be for a community A to automatically boost/repost all posts from a community B, effectively bringing all messages of B into A.

Note that these are pure speculation on my part. I don’t know if any of this is possible 😅

Sounds like what Aral and Laura are building over at https://small-tech.org/

Simple one click install

Single user instances

There’s a ton of content. What are you interested in?