How do I disable controller use?

[GreedyMerchant]

In my game if a controller is connected to the computer and the player hits a button on it the game will assume that the player is using the controller for input. This is a problem since my game doesn't support controllers and I want to stop it from happening. How would I do this?

 

[ChristianWiele]

If you are using the default (old) Unity input system, you have to remove the controller mappings from the Input Manager section of the preferences.
If you are using the new Unity Input System, you can restrict the usage of supported devices:

Input settings | Input System | 1.3.0

docs.unity3d.com