The USB port on your iPad will get a massive update in iOS 13/iPadOS. You will be able to plug in pretty much everything except a printer, and have it Just Work™. We already know this. But what exactly does work when you plug it in? I decided to try it. I took my old test iPad (a 1st-generation iPad Pro) on a tour around various friends’ homes, and plugged stuff in. Here’s what happened.