Left-hand shifter, yep. I did this on my first hacked-together rando bike in 2015.
I never had a bar-end shifter before that, so I learned that way. Feels very natural and allows me to downshift while scrubbing speed with the rear brake (brakes are setup euro way)
Wait till you realise how nice a 46 is!
Out of curiosity, left hand bar end shifter?