I actually managed to get the stadia controller to work and play on xbox series s via remote play and an android phone. (Some reason iphones not working right)
Steps
1. Go to (Stadia.google.com/controller) and update your stadia controller to enable BT switchover.
2. Have a working android phone with xbox app installed and remote play is setup on your Android and xbox series s.
3. Pair the stadia controller to your android phone. (Once connected and paired via BT, you should be able to back out with B button and use the controller to move around on the android phone. If not try re-pairing the controller again until it does)
4. Once controller is paired and working on android open xbox app and start remote play from the app on the Android phone.
5. Once the app connects you should be able to use the controller like normal. *note app must be on at all times and on a charger.
And thats basically it. Hope this helps. Like subscribe and share for future content.
Remote play with stadia controller on ps5 coming soon