If you want a Button to be Selectable, be sure to fill out the Selected section of your Button Styles. My Buttons for selecting a Server or Remapping Key Bindings use these Styles:
Of course, the Selectable checkbox will need to be enabled in the Button’s settings.
I haven’t worked on the TODO note any further since making the Tutorial! I’ll likely need to dig into CommonUI’s code and find how Gamepad inputs are managed. There must be some state or reference deep down to track the last UI Element the Gamepad was “hovering”. Making the Keyboard and Mouse update this state/reference will fix it! In the grand scheme, it’s a pretty small detail.