This thread actually marks an unsolved problem as "accepted"/solved https://developer.apple.com/forums/thread/119265
As of iOS 14/15 Apple's own QuickLook does not support: On iOS and in AR, any USDZ with PNG transparency.
It's a shame and testament to the AR dev team's (in)ability to address this issue.
Multiple tweets and a basic google search shows this problem existing for over 2 years and now entering the third year. Meanwhile formats such as GLTF/GLB... just work
