My issue was just not having it plugged into the correct USB port. I remember having issues with adb/fastboot in the old days where sometimes it is just finicky about which USB port the phone is plugged into
This worked flawlessly for me on Linux. I had to run fastboot as root of course.
I am wondering if anybody has managed to Flash the Stock Android Image and Unroot the device?
Are there instructions for that as well?
If you are referring to Android Generic System Image (GSI), then yes it does work. Infact I just made the GSI instructions public which had been sitting in draft mode.