I think I figured out my "Checking your connection..." problem with Stadia and I wanted to share. I believe it had something to do with Linux.
My solution was basically not start Linux anything after a fresh restart and without any connected peripherals and then start Stadia (not in Incognito), then plug in my USB controller and viola... That process got rid of the "Checking your connection" circle of infinity to finally disappear.
Note that I'm still running the following extensions: Stadia+, uBlock Origin and PiP by Google.
tl:dr - I think it was Linux
@codesplice Yes, I'm talking about the Linux beta on Chromebooks. Everytime I start Stadia with the wired controller connected via USB it get's stuck. If I disconnect the USB controller and reboot, then everything works fine again without using Incognito. I haven't tried to remove Linux entirely because I use it too much.
It's weird but I'm glad to have it working on regular non-Incognito so I don't have to keep inputting my user/pass.
I'm using an Xbox One controller via USB to my Chromebook.
This is really good stuff to know. I use the Linux features heavily on my Chromebooks, and I did run into an issue with not being able to start a Stadia game a couple of weeks ago. It worked after a restart - I guess since I hadn't started the Linux container again before launching Stadia. I don't think I would have made that connection on my own.