For the AR, operations which can be done with the rifle pointed on target are done with the right hand, such the left hand, the support hand, remains able to support the rifle. Mag changes and subsequent chamber charging actions are done by the left hand.
I often shoot right handed bolt rifles left handed, and I will say flat out, it’s an illogical hypothesis to believe a right handed bolt gun should be operated with the left hand (mirror image to what I do). If you’re breaking position between shots, you can get away with whatever manipulation you want, but if you are keeping the rifle shouldered, firing from anything but prone or benched, and staying on the gun, you’re losing ground to use your support hand to manipulate the bolt.