You mention chessable so I would like to shout out my own project. I created listudy[0] that does a lot of the things that chessable does, but is also free open source[1]. On my site I use spaced repetition to memorize openings. Unfortunately there are not many studies on there right now but hopefully this will change in the future. [0] https://listudy.org/ [1] https://github.com/ArneVogel/listudy