Jerboa has some good ideas and features, but it has sadly been consistently the most buggy out of all the clients I've tried, across updates.

I was using Connect until yesterday, which I found to be the best option thus far, but I don't think it's open source. Liftoff is also good though, but in terms of looks something is off with it for me. Maybe it's a little to cluttered.

Sync is fantastic in terms of features, look and feel and customization. It's definitely the best app I've used so far. The issues of free-with-ads and the steep pricing for ad removal/Ultra are definitely there, but I can't deny that it's the best feeling app for Lemmy right now.