At the moment I would say Sync, the level of polish is unmatched in other apps, and it has many customization features as well as being relatively stable and bug free for a beta. The downside is there are ads to support the dev and the cost to remove them is high. Oh and if you absolutely refuse to use non-FOSS then this isn't for you sadly
There's no API at the moment so Artemis is using scraping to get by, but it's not released yet. Ernest (the kbin main dev) is working on an API and app as well. It'll come, but it might still need some weeks.
Maybe give Infinity for Lemmy a shot! I don't have a tablet to test on at the moment but I recall Infinity for Reddit (which this is a fork of) supporting tablets.
Some minor bugs but development is moving quickly. Bazsalanszky is doing an incredible job and I'd personally consider the app to be in a usable state for the average Lemmy user already :)
I am still using connect, but long term I hope the development for "Slide" goes well. That is what I used on my tablet for Reddit and imo it was great.