Thank you Apple for the update! That makes sense... It would be great to have this little detail added to the developer documentation in order to reduce wasted time in trying to get it to work in a dev environment :).

Do App Clip Smart App Banners only work when the app is published? Or should it work when uploaded via TestFlight?

I am not seeing Smart App Banners showing up in iOS 14 release version as well....

For the life of me, I still can't get an App Clip Safari Smart Banner to show with Xcode 12 and iOS 14 release builds. I did all the setup required with adding the AASA file to the webserver, add meta tag to web page, and updated bundle IDs with associated domains...