I'm working on Repple (https://repple.sh)! It's a modern spaced repetition x incremental reading/PDF library app with a few (tasteful!) QOL AI features.
I've been using Anki for 10+ years and love it but always wanted something with a cleaner UX and a reader view. The recent Anki ownership change pushed me to finally make something, and it's seeing some traction :)
Right now I'm focusing on getting the reading and note-taking view to be nice. I used to use Polar Bookshelf (RIP) but that went away, trying to make something better.
The flashcard side also has a REST API btw!