QMK has been the most joyful open source thing I've ever used. Typing on my second split keyboard with weird chording right now. I've seen a spike in rotary encoder support lately (on the Planck and an upcoming new version of Keebio's Iris-the old version of which I'm using now) so keep an eye out for that if you're into fun extra input methods on your keyboard. I'm looking forward to having etch-a-sketch style arrows, personally.