Hey,
it's me again.
I guess I am a bit closer. I was wondering why my custom gamepad driver which generates a uinput device is not working. By incident I started the game directly without the start script, so I could see the information output. One of the very first lines was "couldn't find keyboard event file". I recognized that my custom driver creates a eventX in /dev/input but not in the subdirectories by-id or by-path.
So I tried to create a symbolic link in by-id, pointing at my event.
Now the keyboard-emulating gamepad worked in the game!
Playing that a bit further I went back to my gamepad driver which behaves like a gamepad without keyboard emulation. Running on top xboxdrv with mouse and keyboard emulation. again with a symlink in by-id.
Now the regular gamepad-driver with xboxdrv on top worked in the game!
Only point is, that no regular keyboard is allow to be connected (maybe be game only uses the first keyboard?).
BR
Florian