Retroarch does not recognise my controller

Despite have autoconfig setup for input device, the Retroarch snap on Ubuntu 18.04 would not work with my cheap PS3 like controller.

Turns out this is a disconnect between the snap and USB gamepad\joystick support:
https://forums.libretro.com/t/retroarch-does-not-recognize-my-usb-controller-solved/16985

You need to connect the controls to the snap using:

• sudo snap connect retroarch:raw-usb
• sudo snap connect retroarch:joystick

Thanks hunterk!