we find that lefties (my wife is leftie, I am Rightie) that we have taught have no difficulty in playing right handed on a number of instruments including fiddle guitar and keyboard provided they have never played before.

We both teach, and advise the use of standard instruments where possible for a variety of reasons already mentioned.

If someone has played left handed even for a very short time, they are then (in our experience) committed to that way round.

The eventual style of the player does seem to change according to which role the dominant hand takes