Jerboah actually. Its the most complete, stable and looks very good. Used Thunder but it lacks features and is kinda buggy. I was hyped about Infinity, but I only really needed Infinity to have private subscriptions and multi accounts, which I dont have on Lemmy.
I mean its search is limited to finding communities and we can't really search for posts, users or comments using keywords. Sadly, among FOSS apps only eternity has a decent search functionality but it's still under development and lil buggy. Liftoff does categorize searches but doesn't have the functionality of searching within communities.
So far only Boost, Sync and Connect seem to have it and none of them is open source.