It might be a good feature/option of a frontend to automatically aggregate same-name communities across federated servers. Bogus actors would either be downvoted or defederated off the feed.

Lemmy pretty much just needs tags. Like you can mark your different “technology” communities with the tag “technology” and a user can subscribe to this tag to view all posts from whatever communities have this tag (and they don’t have to call themselves strictly just “technology”)

Something like that I would imagine so no direct interaction between communities required.