Add Multiple Bluetooth Controllers to Unity using PC

Connect controllers to bluetooth on PC

In Unity – New Project
Window > Package Manager > Input System > Install

Select Yes:

Add the asset:

https://assetstore.unity.com/packages/tools/input-management/controller-tester-43621

Map Axis 1

To try multiple controllers, import the SimpleMultiplayer project:

As each controller provides input, it splits the screen automatically and shows each player their own camera / pane