I have tried wifi and wired chromecast ultra, I can play any games as it keeps telling me my connection is not good enough. However ma pc connected to same network right next to CCU gets 600mb (I have ATT fiber) and my phone on wifi gets 507mb. Like I said tried wifi and ethernet on the CC ultra but can't get past.....
On any device? CCU, Browser, phone.. etc?
I have the same issue
Stadia speedtest : 9 M
speedtest.net : 128M
it works on my professional computer and phone (same wifi, same browser)