Would you ever consider adding Chinese?
There is tons of great open source data out already, like https://github.com/chanind/hanzi-writer?tab=readme-ov-file and https://github.com/skishore/makemeahanzi and given you already have Ringotan put together, I wonder if feeding this data in wouldn’t be fairly trivial. I can ALMOST replicate Ringotan-like function using this tool https://github.com/krmanik/Anki-xiehanzi to pull from those resources into an Anki deck, but by default they're teaching hanzi by having you draw over the outlines instead of testing you on hanzi like Ringotan does with kanji. I spent a few hours trying to duct tape my way into a solitution, to mixed results. But even if I managed to get it working perfectly, I like the algorithm in Ringotan more than anything else I’ve tried and considering the main tool that's already put together for this (Skritter) is a ridiculous $15 a month or almost $200 a year on subscription, I would be very happy to pay something to see this done.