In mobile design, I generally stay with the same convention of placing positive actions on the right. The "dominant hand" argument isn't relevant, since your thumb usually rests on the left side of the screen if you're right-handed, but the "forward motion" rationale still makes sense.

It will be interesting to see what conventions from Windows-Icons-Menus-Pointer (WIMP) interfaces still exist on mobile in ten years, when desktop UIs are mostly history.

We still type on QWERTY keyboards, even though the original rationale is long gone; musicians still make albums about an hour long even though they don't have to fit on two sides of a vinyl record anymore; we still have 60 minutes in an hour even though the ancient Babylonians' base 60 counting system has been gone for millennia.

I wonder how many more generations will continue to debate whether "cancel" should go on the left or the right?

I'm right-handed, but for decades have used the phone in my left hand -- I found this to be useful at an early job that often required taking notes whilst on the phone, so I optimised behaviour for that and the habit stuck.

When early cellphones came along I had no trouble using my left hand only when most "right-ies" I know used them with the right hand. Since smartphones became popular I still phone with my left hand primarily, though I have become more ambidextrous with it, and I've noticed that others seem to switch hands more too.

I don't know if handedness does has much influence to such clumsy devices like smartphones. It's not comparable to writing text by hand, where much greater precision is required.

I alternate; sometimes left, sometimes right.