how many hands can you use.. and how many fingers.
In my case, both hands, though only:
* Left index and middle finger
* Left thumb
* Occasional assist from the left ring finger. I can't really control it, and it sometimes causes typos.
* Occasional assist from the right middle finger. Same as above.
With regard to split layouts, there hasn't been one yet that agrees with my hands on where the "dividing line" should be. And even when I think I know, my hands have proved me wrong every time I try to type on one.
If we're talking health, this I know to be true, for me personally: If I were FORCED for health reasons to what is considered an ergonomic keyboard, I would sooner give up all typing and learn to use voice-control software, with all its frustrations and foibles, than to invest 5 seconds trying to retrain my hands. Trust me. I know my cerebral palsy well enough to know what's worth my time.