There's all kinds of text keyboard mappings including some like court reporter's input devices.

i don't actually know a lot about split/ergo/mech's and don't know of any non-rabbit-holey info sites but you can learn a bit about 1 and 2 handed split ergo's and ZMK/QMK firmware mappings at https://old.reddit.com/r/ErgoMechKeyboards/

ZMK's docs are pretty good https://zmk.dev/docs/keymaps