Hey there, sorry for the late reply.
I actually gave up. There is sadly no native support in my Unreal project. To this day I dont know how a HTML5 based gamepad-tester-website having no issues with reading the controller and Unreal’s RawInput method completely refuses to work at all. I tried reading different channels, installing weird out-dated and discontinued DJI Software, nothing helped.
My non-educated guess would be, that RawInput expects only linear values and the controller sends data in a different format. If someone reads this (probably not) I would recommend to brute force Unreal to recognize the controller as a controller. Everyone else, even windows, doesnt have issues with it.
My solution in the end was the Xbox 360 Controller Emulator called “X360CE”. And yet again a software released in 2011 having no issues reading the controller. Just Unreal doesnt know what to do. Its just bananas.