I can confirm, it doesn't work right now. With this example, https://raw.githack.com/immersive-web/model-element/main/examples/index.html in macOS M1 I get a blank rectangle: and in visionOS I get the image fallback: I do see that model.constructor is HTMLModelElement, and model.getCamera() eventually gives the error Unhandled Promise Rejection: undefined so the API is there, just not working yet It is experimental behind a flag, so the WebKit team may still be ironing out the details.

For reference in case the above example stops being available or changes, this example is permanently available since time of writing: https://rawcdn.githack.com/immersive-web/model-element/ed579b5ad3fdca3bca2805e182624a23d367b534/examples/assets/FlightHelmet.usdz