If you’re switching to the new Unity Input System and using Visual Studio code, you’ll probably hit the hiccup I did.
After switching back-ends, you’ll find that you’re not able to use the new namespace. If you try, you’ll get “namespace not found.”
using UnityEngine.InputSystem;
To fix this, you’ll simply need to create the csproj file so VS Code knows to use the new assembly.
In Unity Editor go to Edit->Preferences
Choose “External Tools”
Click the “Regenerate project files” button
After that, VS Code should recognize the new UnityEngine.InputSystem namespace!