Pleonasm

Sure, I also have been trying to learn about how Lenmy works. I haven't yet found a comprehensive overview that details everything though.

From https://join-lemmy.org/docs/administration/federation_getting_started.html

If you search for a community first time, 20 posts are fetched initially. Only if a least one user on your instance subscribes to the remote community, will the community send updates to your instance. Updates include:

New posts, comments Votes Post, comment edits and deletions Mod actions

From: https://join-lemmy.org/docs/users/01-getting-started.html

These previous ways will only show communities that are already known to the instance. Especially if you joined a small or inactive Lemmy instance, there will be few communities to discover.

This issue/post on github has some info: https://github.com/LemmyNet/lemmy/issues/3062

I would also checkout some discussions on [email protected] [email protected] https://selfhosted.forum

As far as I understand, your instance is only aware of a community on another instance if at least one user on your instance has subscribed to that community on the other instance. Perhaps that's what you're experiencing?

So if you're the only user (let's assume for ease) then, that represents all the updates (posts, comments, votes) from each community that you are subscribed to?

That seems high when you extrapolate that to 10000 users, like a larger instance might have.

I think from the point of view of speed/ease of development, the webapp makes more sense for now. Once it's more stable, perhaps a native app is worth trying for performance reasons.