It’s a Lemmy front end, very clean. On your local device it runs some algorithm that tries curate a better feed for you based on your interactions with Lemmy. Not unlike many larger social media sites.
You can also sort by the normal filters like ‘active’, ‘new’, etc.
I read about it burried in some comments.
It’s great to see so many front ends and experimentation within the Fediverse.
Another interesting frontend is tesseract.dubvee.org which has some clever features, and good mod tools.
The Thunder app is still my number one candidate.