Out of curiosity, what content are you looking for? Discovery on Lemmy can be a problem, but sometimes the communities are there and even active, just buried.
But may I also suggest searching by Top Day/12-hour/6-hour to see the most active posts. Lemmy’s scaled algorithm still doesn’t get it quite right IMO.
It looks like there are instructions here about hosting your own flatpak instance: https://docs.flatpak.org/en/latest/hosting-a-repository.html