This is the zmk shield definition for the original Ergodox. It uses a teensy2nicenano adaptor PCB.
This is not using mainline ZMK, instead it uses kscan read by port PR in order to have a responsive keyboard. This is because reading a key at a time from the MCP2038 IO Expander over i2c is much too slow.
As of Feb 2023, the keymap is miryoku inspired, but sort of halfway between an ergodox and a corne. Specifically it still has shift keys, and numbers, but it does use home row mods.