After some searching, I have finally figured out how to enable gamepad support in Steam for Linux. Sometimes Steam has trouble locating button map configurations for older controllers so a manual set up is required. Set up is easy, but unusually hard to find. Here is how it’s done:
1. Enter Big Picture Mode
In the top-right corner of the Steam interface is a button to enter Big Picture Mode. Click it.
2. Enter The Settings Menu
Click on the gear icon in the top right.
3. Enter The Controller Settings Menu
Click on the Controller menu item.
4. Choose The Appropriate Controller
Now you will be presented with a list of detected controllers. Choose the one you want from the list. If your controller doesn’t show up here then try rebooting your computer with it plugged in. If that doesn’t work then I can’t help you ☹
5. Setup The Controller and Enjoy!
Now set up your controller button map and start playing. This part shouldn’t need any explanation so I’ll leave you to it.
Well that was harder than it should be. I’m not sure why they don’t make the controller settings accessible from the main window but at least it can be done.
Happy gaming! 凸(-_-)凸