I am more interested in the workflow of using one separate keyboard for each hand.
That is probably trivial to setup on conventional keyboards but I wonder if it is ergonomically better.
Splitting a keyboard has ergonomic benefits. I don't see that "full keyboard for each hand" would be an advantage. One of the more popular split keyboards is the Corne Keyboard.
https://github.com/foostan/crkbd
There are split keyboards with more keys than the Corne, such as the Lily58. https://github.com/kata0510/Lily58