Is there a way (when user clicks webxr download option) to download/install this in background while the user is not leaving the AR-app?
No. WebXR Viewer should be installed like any other app in iOS, from the App Store. That’s iOS…
Puzzles and JS. Fast and expensive.
If you don’t see the meaning in something it primarily means that you just don’t see it but not the absence of meaning at all.