Others have mentioned Materialistic and Glider. Both are great options that I used for a few years. However, I've recently changed to Hacki. It's also in the core F-Droid repo and works great for me as a HN client. Since it will even try to notify you of replies
I love it, releases on GitHub to so I can avoid F-Droid builds. Dev is nice and receptive too and the app is feature filled.
Finally replaced Materialistic for me.
This is what I often use, though I have noticed some weirdness where votes won't stick despite the app saying that they did and comment threads that are too big constantly refresh until all the comments are loaded. Might give some of the other apps in this thread a try.
Thanks a lot for open-sourcing it.
I wait for the day, where I can finally get a good HN client at F-Droid :)