Emulator

I also have the same problems for several months now since I was forced to upgrade to the master branch because dolphin was crashing after a couple of seconds after a game was loaded when I upgraded my OS to Ubuntu 18.04.

So I did just did a bisect of the code and the problem appeared with this commits:
[[https://github.com/dolphin-emu/dolphin/commit/694df74b0bd535649c48b895faea54c9c95d1d6d]]
Was merged to the master branch in the following pull request:
[[https://github.com/dolphin-emu/dolphin/pull/6331]]

Now, this is where Dolphin was switched from the WxWidgets GUI to the new Qt one, so that's a pretty big change. I could see two reasons why the Steam Controller would not work : either the input handling is completely different between the old WxWidget and new Qt code or the way the game window is created is incompatible with Steam game detection.

The second part is probably what happens. For the Steam Controller to work correctly, Dolphin must be launched by the Steam client. By default, when we are in the main Gui, the Steam Controller is in an "emulated" mode where it simulates XInput Mouse and Keyboard. The controller is only switched to gamepad mode when Steam detects a fullscreen window.

Following my findings, I did a couple more tests with the controller configuration. I was able to get the controller working correctly with Dolphin by modifying the "Desktop Configuration" of the controller to the "Gamepad" template (must use Big Picture Mode to modify that configuration).

That means that the Steam Controller is always recognized as a Gamepad, so no more mouse and keyboard emulation. This is a documented issue with buggy games that do not handle correctly the fact that the Steam Controller is both a gamepad and a mouse / keyboard at the same time.

Confirming that this issue still persists as of 5.0-c484276-dirty within Ubuntu 18.04.3 The Steam Controller is read as a Keyboard device (Specifically XInput2/0/Virtual core pointer) unless specified as a Gamepad in the Desktop Configuration within Steam, per mbouchar's suggestion. Compared with a Logitech F310 which is read properly without configuration. A similar issue was present in Windows and circumvented by booting the game, which allowed the controller to be read as a gamepad; this same method did not work in Ubuntu on the same hardware. Can also confirm the Libretro core version (1fbd599) works as intended. Will continue testing, but somebody please investigate a fix.