Python Virtual device isn't properly recognised by steam

Question

I'm trying to create a virtual joystick device for use in steam games, on Linux (specifically Manjaro). I'm using Python for this project and have tried with both the evdev and uinput libraries, with the same result: The system seems to recognize the device (/dev/input/ files correctly created, evdev and jscal all work correctly, etc), but steam doesn't accept it as a valid controller. This is the code I'm using to test it:

#!/bin/python

import uinput
import time

def main():
    events = (
        uinput.BTN_JOYSTICK,
        uinput.ABS_X + (0, 255, 0, 0),
        uinput.ABS_Y + (0, 255, 0, 0),
        )

    with uinput.Device(events) as device:
        for i in range(20):
            device.emit(uinput.ABS_X, 5, syn=False)
            device.emit(uinput.ABS_Y, 5)
            time.sleep(2)
        device.emit_click(uinput.BTN_JOYSTICK)

if __name__ == "__main__":
    main()

Running steam in console, I get the following output when a physical controller is connected:

Local Device Found
  type: 046d ca04
  path: sdl://0
  serial_number:  - 0
  Manufacturer: 
  Product:      dev:xb1:Logitech Logitech Racing Wheel
  Release:      110
  Interface:    -1

!! Steam controller device opened for index 0.
Steam Controller reserving XInput slot 0
Controller 0 connected, configuring it now...
Installing breakpad exception handler for appid(steam)/version(1576908998)
Controller has an Invalid or missing unit serial number, setting to '46d-ca04-655a04e'
!! Controller 0 attributes:
  Type: 32
  ProductID: 51716
  Serial: 46d-ca04-655a04e
  Capabilities: 0018414f
  Firmware Version: 0
  Firmware Build Time: 2147483647 (Tue, 19 Jan 2038 03:14:07 GMT)
  Bootloader Build Time: 2147483647 (Tue, 19 Jan 2038 03:14:07 GMT)

Opted-in Controller Mask for AppId 413080: f
Loaded Config for Local Selection Path for App ID 413080, Controller 0
[413080]Non-Steam Controller Configs Enabled: 1
!! Controller 0 attributes:
  Type: 32
  ProductID: 51716
  Serial: 46d-ca04-655a04e
  Capabilities: 0018414f
  Firmware Version: 0
  Firmware Build Time: 2147483647 (Tue, 19 Jan 2038 03:14:07 GMT)
  Bootloader Build Time: 2147483647 (Tue, 19 Jan 2038 03:14:07 GMT)
Fetching Config Sets 0

However when I create the virtual device, I get the following output:

Local Device Found
  type: 0001 0001
  path: sdl://2
  serial_number:  - 0
  Manufacturer: 
  Product:      python-uinput
  Release:      0
  Interface:    -1

Local Device Found
  type: 0001 0001
  path: sdl://2
  serial_number:  - 0
  Manufacturer: 
  Product:      python-uinput
  Release:      0
  Interface:    -1

So steam seems to be correctly detecting the device, but not recognizing it as a valid game controller. I've tried changing all the details of the device (name, type, product, etc) to match an existing physical device with no luck. It does output the "Local Device Found" twice for the virtual device and only once for the physical one, I'm not sure if that's relevant or what's causing it.

Thanks in Advance