Not sure how many of these are open-source but it's a good start
https://github.com/dbeley/awesome-lemmy#mobile-apps
You can also "install" the mobile web version as an app. Just go to your home instance lemmy.one and and fromthe menu on your phone's browser, there's usually an install button.
This also works for Voyager, https://vger.app/posts/lemmy.one/all
Jerboa is made by Lemmy's developers, and is free, open-source software, meaning no advertising, monetizing, or venture capital, ever. Your donations directly support full-time development of the project.
https://github.com/dessalines/jerboa
I guess they want a different open source client.
I've tried Liftoff (fork of Lemmur that is actually maintained and pretty great) and Thunder as well as Jeroba and Lemmur, they're both better.
Thunder is very iOS-esque and plain, Liftoff has the weird bottom layout Lemmur does, and inherits some strange UX quirks from it such as not storing last sorting preference, not having "block community" in the hamburger menu for posts, and sorting replies by "hot". Itst actively maintained so I'm sure it will improve, and it's the most stable and useful mobile Lemmy client I've tried so far.
I have not tried any closed source clients and will not do so.
Liftoff is a great app to use! The only downside is that Liftoff gives no sign that you were automatically logged off. Nothing is more fun than writing a message and being greeted by a message "error: not signed in" lol
The most polished native Android app is Thunder imo. If you are ok with PWAs, then Voyager is currently even better than Thunder
Just a silly thought here, are you by any chance using a service like NextDNS? I couldn’t access lemmy.world because it was blocking domains newer than 1 month old, once I disabled it everything was ok.