Sync because I had huge preference for apps that followed MD3/Material You. I wish it had an inline comment editor for replying in the middle of threads, that was my only missing feature. Slide did the inline editor nicely.
Apollo. Everyone in my house did. Two have stopped using reddit entirely, I'm still checking on a couple of communities until their counterparts take off here. I'm using Dystopia there now because I'll never, ever download their shitty app.
Relay for Reddit, which was called Reddit News back in the day. I'm aware it still works; dbrady is developing support for subscriptions for those who want that.
I'm going back and forth between Connect and Thunder for Lemmy. Connect seems most like Relay, but they're both good.
BaconReader. I didn't shop around. I just downloaded one, liked it enough, and it never gave me reason to go hunting for something different. Unlike the official app, which was one my phone for all of maybe a day.
Slide. It was open source and available on f-droid. It had been a while since the last update and some features were long longer working (in-app YouTube Playback). But I would just open in browser things that didn't work.
It was very easy to use and highly customizable, which is why I used it. And zero ads. Can't stand ads of any kind.
Relay. And I still miss it. Better than any of the other apps I've tried for reddit or lemmy. Very smart design and UX that made it far more usable and enjoyable.
Back when I was on iOS, I started with Alien Blue, then I moved to Apollo when reddit purchased it.
After I switched to android, I settled on Sync and Boost. I used Sync about 90% of the time but I had my alts on Boost and would have different feeds split between the apps. The last few versions of Boost had gotten me to start thinking about using it more but then the API changes were announced.
I was using Narwhal, which may or may not have survived. I had been under the assumption it was going away, but June 30 I stopped by the subreddit and apparently the developer was working with Reddit to move to a subscription model or something. Even though my 3rd party app has apparently survived, I walked away and deleted all my comments/accounts.