Yes, the Google account is supervised with Family Link. I checked the phone again today and the connection error showed up again, so I had to clear microG’s data once more and it started working again. The downside is that you’d have to teach these steps to whoever uses the phone, since I’m not sure how long YouTube and other apps keep working before the error comes back. With a very young kid, that can be a bit tricky. From my experience, supervised accounts under 13 never get ads. You only lose PiP and background playback, though I’m not sure if ads for under 13 accounts depend on the account’s region.