Loving itch.io as a Linux gamer this is adding even more games to my growing library (and backlog). A lot of sites and services do no offer what I am going to suggest but I hope that itch.io would be the first.

I use STEAM, GOG, Humble Bundle, Bundle Stars, GameJolt, Yoyo Games and others.

All of these inform users that their games have gamepad support.

I've been looking for some more details - not in terms of which brand of gamepads are supported but what button layout does the game support.

Something like

2 button gamepads - directional + 2 action buttons

3 buttons gamepads - directional + 3 action buttons

so forth

6 button gamepads - directional + 6 buttons

twinstick gamepads - with x buttons needed

and more.