While I'm only a collaborator and not a maintainer, your second question is kind of reality already since there's a UI rewrite in a very early state to use leptos instead of infernojs.

1. The biggest ones I can think of, are the re-write of the UI in rust / leptos, and notifications using unified push. Those will both be a ton of work, and its going to be hard to carve out time to complete them.
2. The back end has gone through plenty of refactors, and we place an emphasis on code maintenance, so its stayed up-to-date. The back-end and DB stack all seems future-proof so far, so I wouldn't change anything.

Thanks!

• Private communities would be good to have, problem is that they will require changes to all parts of the code which makes it very complex to implement.
• I certainly wouldnt have to rewrite the federation code so often if I already knew how to do it.