https://support.google.com/stadia/answer/9595943
All I can see is that for playing in the chrome browser on a PC you should open/forward ports 44700 - 44899. Most of these seem closed on my router according to https://www.yougetsignal.com/tools/open-ports/. Haven't tried all 200 though.
So for someone less tech savvy, should we forward these ports to any specific chrome port, or just the same span on my internal ip?