I have a basic USB controller that I have been using on my Switch, it plugs into the USB port of the dock, and works fine. How/can I use this controller with Stadia. I'm playing via Chromebrowser. When I plug the controller in, nothing seems to happen, but when I pull it out I get a notification bar on the left side saying "Link a controller" so this tells me that it can at least see it. When I click on the controller icon, it just tells me that wireless controllers aren't supported but can be used in wired mode.
Any help would be appreciated
Officially, you can see the compatible controller for Stadia on the following link: https://support.google.com/stadia/answer/9578631?hl=en
You can try to search for other controllers, but I can see most are Bluetooth one.