I think Boost gets recommended often for good reason. Even if it isn't using existing code, design-wise it likely still would be the furthest developed Lemmy app since he's worked on the Boost for Reddit app for so long.

As of right now, I think it may only be missing specifically hide on read. However it does have mark and dim on read in the settings, and for now the Mute dialogue option is a fine alternative.

Unfortunately it's not FOSS, but it's just a single dev from Portugal and paying for the app removes any tracking present from the ads.