Thankfully the lemmy developers are aware of those issues and are working on improvements.
Looks like soon, viewing content will always be done through your instance and links won’t take you to other instances. The clunky way to search for communities on other instances if your current instance doesn’t know about them yet will get fixed too.
Multireddit style aggregations of communities are also being worked on
Plus these days there is a massive influx of users, once this stabilizes a bit all major instances will be federated and know about communities on each other, so many problems of discovery will get mitigated.
I also run a self hosted instance so I would be interested in a bot that stays subscribed to communities I want “synced” into my instance without me also being subscribed