After upgrading to 11.1 from Catalina, Wi-Fi became unusable on my late 2014 iMac 5K. At first I tought was my router... (never had any kind of problem before) after some tests, ended that the problem was the OS upgrade. Connection drops frequently, ping goes high and low. Stadia totally unusable; via Chromecast is perfect. Really hope tha 11.2 fix this terrible bug...
You should check if you have location services enabled, there is a known issue with MacOs where in order to find the location it temporarily disables the wifi every once and then, you can check also this post on reddit https://www.reddit.com/r/Stadia/comments/eet8f1/psa_disable_location_services_while_playing/ where they explain how to disable the service