I’m relatively ambidextrous anyway, but I’ve trained myself to be able to mouse with either hand. It started as a way to combat carpal tunnel. I can use a mouse, trackball, or stylus with either hand. I can’t draw with my left hand, but I can do anything that doesn’t require fine precision.
It’s actually a pretty useful skill, because I often have to use the number pad and that way I don’t have to switch from mouse to keyboard. It does force me to be more selective when buying trackballs.