Why not use QMK [1]? Both of the author's keyboards (Anne Pro 2 and a TADA68) support QMK, there's a lot more to do with QMK, and it's on the keyboard itself.
QMK is not great, honestly, IMO. It’s very constrained in what it can do, especially without having to recompile, and a lot of it depends on your keyboard.
[1]: https://qmk.fm/