I have shared this issue privately with Herbst but making a public issue to track it here in case anyone else notices it - I have found that setting alpha clip for a material using Volume + Thickness causes it to not export in Quick Look currently. I have some example links I can share privately from a working project. This issue is not there in Needle Engine for Unity 3.22.6 so at some point after that version this regression in Quick Look USD export happened.
by user 103054507105067008
Hello there – we have an experimental AI bot 
that might be able to help you with your question. Would you like to try this out?
Thanks - I’m aware 
Most likely reason is some adjustments we did how opacity is multiplied into textures to fix issues with QuickLook, and alpha test cases may be affected
If you’re feeling experimental you can also adjust code in ThreeUSDZExporter, it’s relatively straight forward to do so
@herbst🌵 I am now working again on a project this affects - is it possible for me to script up something that can exclude one material or object from being multiplied into those textures?
by user 103054507105067008
Same answer still, feel free to adjust the code for that usecase.
I’m back in office for literally two hours^^ and hope to get to look at your issue latest on Monday
Thank you, will be looking into that on monday also, have a great weekend
by user 103054507105067008
@herbst🌵 Did you get any time to look into this yet? Thanks for your help so far
by user 103054507105067008