I have the same issue. Although there is one 'workaround' - I am able to start the game in chromecast via iOS app and it works well after that. But have to do it each time I turn on chromecast/controller.
Tried multiple different tips for resolving this, but no avail. The only one I could not try is linking via android stadia app (just do not have one). So in my case this seems to be a bug specific to an iOS app. Hopefully it gets fixed eventually.
Let me know if you need any advice with the other tips - maybe your case is different and you can make it work. Also funny how many of those reports are here and no one seems to react to them.