I only found the Connect app able to hide read topics, while Jerboa and Liftoff does not have this feature. Is read status built-in into Lemmy protocol?
From my understanding, Lemmy is software, while ActivityPub is the underlying protocol. Mastodon, Pixelfed and Kbin are other softwares running with the ActivityPub protocol.
Jerboa has the setting you request under Settings > [username] Settings > Hide Read Posts
That must mean ActivityPub tracks read status and provides it. Just look deeper in the settings.
Thanks for pointing out the read settings on Jerboa, it works. And it affects on Liftoff too, those that I read on Jerboa won't appear on Liftoff anymore, but Liftoff does not make read status from within it app.
Lemmy, being part of the ActivityPub fediverse should have that capability, if not now, then real soon. Remember that Lemmy is still quite young and growing. I foresee great things for it in the future.
Some developers were asking whether it was acceptable to use that API call since it would be a lot of server traffic (especially if scrolling past counts as read, which is an option in connect) - so if apps don't all support this feature yet, that might be the technical discussion they're trying to figure out.