Hi how i can check if sometime my stadia use wifi over ethernet ?
Sometime i have really choppy expérience and i think thats because my stadia use my wifi instead.
I assume you mean the Chromecast and not a PC.
Chromecast/Stadia interface doesn't tell you which connection type is being used (right now, anyway). You have to go into the Google Home app on your phone, find your Chromecast and check the MAC address then look up in your router to see if it is connected via WiFi or not. Unfortunately I can't think of a more convenient method of checking this as there is no clear indication even in the Home app about whether it's currently connected to WiFi or Ethernet unless I'm missing something.
Actually, in the Home app if your Chromecast Ultra is connected via Ethernet the WiFi setting is simply not shown on the device settings screen so you can just use that as your indicator. If you see WiFi settings at all, it probably means you're not utilizing the Ethernet connection.
Though it would be extremely odd for an ethernet connection to be unreliable once it's hooked up and working.
What if you factory reset your CCU and never connect it to WiFi? If it has Ethernet during initial setup does it even ask for WiFi info?