Hello, 
I’m back to raise an issue that has been present in Unreal Engine since 4.27. Every Mac developer who I’ve contacted has confirmed that local coop continues to be impossible with Unreal Engine on Apple platforms.
The source of the problem is that additional gamepads beyond the first are not recognized in the editor or in the game. I’ve tested this myself with Xbox, Playstation, and third-party gamepads in UE 4.27, 5.0, 5.1, 5.2, and 5.3. In versions of Unreal Engine before 4.27, multiple gamepads functioned as expected.
To test this, it’s as easy as connecting two gamepads to a Mac, and using any of the key-detection buttons in the editor, such as in an enhanced input context asset. It will be observed that Unreal will only detect the inputs of the first gamepad.
Most tragically, this problem is preserved in any builds and on every Apple platform I’ve tested, including tvOS, and iOS. 
Over the years since 4.27, I’ve posted here, on Discord, and in the Unreal Engine bug report. Once I even had an Epic employee’s eyes on the issue but they were laid off before it could be solved. 
If anyone has any idea how to solve this, or how to raise this issue higher, please let me know. We’re desperate for a solution to this problem that is relevant for anyone developing coop games for Apple platforms.
Cheers.