The current 1.3 mobile version does not support controllers. Any videos showing it working are either custom or a hack.That doesn't make sense, as I have observed on iPad OS 13 (perhaps you refer to all ios, and I was specifically speaking of iPad OS) an Xbox controller being used.
If your friend is using a controller for Terraria mobile, they are using some sort of hack or external tool. I will repeat myself: Terraria 1.3 Mobile does not support controllers.I didn't see a video. One of my friends was doing it on the iPad OS beta 1 at school with his Xbox controller.
1.2 Did have controller support, but it was lost when the app was rewritten for 1.3.Did 1.2 then? I know for a fact that they didn't use anything apart form an Xbox 1s controller, and they also let me try it on my iPad after installing the beta.
This is also not any special controller for the iPad. This one has also been used for playtesting a game I coded on pc, so we can conclude that it is a regular controller.