Can you aim a handgun with your off hand?
I’d be pretty screwed if I couldn’t.
The short answer is: yes, you can train yourself to switch hands with firearms. For a lot of shooters, myself included, this is a fairly important skill, because many guns are designed for right-handed users. In some cases, the fire controls (safety, fire select, magazine release, ect) only on one side. In other cases, the grip and or stock will be contoured for the right hand, and attempting to use one of these with your left hand will be unpleasant or impossible.
What this won’t do is help you dual wield handguns. That really doesn’t work. Guns are, still, two handed weapons. You need your second hand to stabilize and manage reloading. So you’re sacrificing accuracy to burn ammo faster, for no real benefit. More than that, you really can’t sight two pistols at the same time. Getting them in line with your eyes will put the barrels way too close to one another, resulting in bashing the guns into each other when firing in tandem. This is one of the few situations where a laser could be useful, but even just the longer reloads, and loss of precision, mean dual wielding isn’t advantageous.
One variety of dual wielding that was entirely viable, was a sword and pistol combo. This was more common in the 17th and 18th centuries, with inaccurate, single shot firearms. During naval boarding actions, and other close quarters combat situations, it was fairly common to fire a shot from a pistol, before following with the sword. In these cases, the pistol would usually be carried in the off hand, with the sword in the dominant one, because it is far easier to shoot with your off hand, than it is to wield a sword in your off hand.
With firearms in modern situations, it can be advantageous to switch hands for a number of reasons. The specific example that comes to mind is cornering. When turning a corner to your right, if possible, you want your firearm in your left hand. This will give you a clear line of fire, while minimizing your exposure. Conversely, when cornering to the left, you want the firearm in your right hand for the same reason.
Being able to switch hands fluidly in a CQC situation is one of the many ways some gun disarms can go wrong. Many disarms rely on locking up gunman’s dominant arm. Against a shooter who has significant experience switching their weapon between hands, these techniques can quickly turn lethal for the person attempting the disarm.
So, yeah, I can shoot off hand. I’m not particularly accurate with my right hand when operating a pistol (I’m fine firing rifles right handed, go figure), but that’s just a personal issue.