We just added Alexandrite to the server, it's an alternative UI for Lemmy created by Sheodox who worked tirelessly to make the necessary changes to we could host it ourselves here. So go to https://a.lemmy.world and have a look!
He continues to update it constantly, you can follow the development on his github page or in his community. If you like what you see and want to support him, why not buy him a coffee? :)
For those who don't have Lemmy World as their home instance and want to use Alexandrite, either ask your instance admins to add it or go to https://alexandrite.app!
Very cool, though it is not very usable on mobile (the popup/modal when viewing posts is just too narrow).
Another new alternative UI for Lemmy is Photon, which I've been contributing to for the past week. It is still early days, but it is usable (I am currently daily driving it using the compact view that I implemented) and is constantly improving.