With the help of Tandem Mode, you can connect another gamepad to your wirelessly paired Stadia Controller over USB-C.
Stadia Controller Gets ‘Tandem Mode’
According to you can “use either controller to play games on Stadia, or both at the same time.” Tandem Mode is “an early, experimental version of this feature that is intended to expand the input device options for Stadia players.” currently, it is supporting other Stadia Controllers, the Xbox Adaptive Controller, Xbox One Elite Controller (Series 1 and 2), and Sony DualShock 4. This new addition comes with two main advantages.
First, it allows you to use select third-party controllers with Stadia, regardless if they can be connected to the device you’re playing Stadia on. Second, it’s easier for those who are physically disabled to play Stadia, since Google is supporting the Xbox Adaptive Controller.
If the linked controller has a Type-C connector, users would be able to use a regular C-to-C cable, otherwise, they will need an adapter or special cable. Recommended Reading: NBA 2K21 is Now Available on Google Stadia