Linden Lab should have no trouble integrating this (on iOS and ipadOS anyway) as Apple provides a Game Controller Framework API. All they need to do is look at the developer documentation and implement it:

It would be great to have this in the Desktop viewer as well as the Mobile viewer. It could even work in the Browser based viewer in the way that other game streaming services support Game Controllers in the browser.

I would also like to see keyboard and touchpad movement support being added to the viewer on iPadOS so that I can walk around using my Magic Keyboard or bluetooth keyboard when playing through the mobile viewer on iPad. Currently; arrow keys and WASD don’t do anything in terms of movement, I have to use the on-screen joystick to move around on iPad. Apple’s Game Controller framework should make adding keyboard movement support easy to integrate into the mobile viewer as well.

Gamepad support + full keyboard and mouse/trackpad support on mobile would be great!