I’m sure this varies from person to person, but I found it quite difficult. Some months ago, I began having bad pain and swelling in my left hand. I thought for a while that i would no longer be able to use my left hand to play, as my fingers were too stiff to finger the note. I would generally have a period of flexibility in the evening, but the flexible window got smaller and smaller. So I got a cheap left-hand violin and started experimenting with it. To me, it was like playing a completely different instrument. I felt like I might as well be playing banjo or bazouki, as nothing seemed to carry over from my knowledge (beginner level0 of right-hand violin playing. Fortunately, my left hand flexibility has been restored with arthritis treatment. I think if I ever lost function in the left hand again, I would be more likely to turn to trumpet or some other instrument instead of left-hand violin. To me, it felt very awkward to bow with the left hand.
This is just my experience; I know that others have successfully transitioned from right-hand to left-hand playing.