Which demo did you try? The car configurator? Also if you're using Firefox, WebGPU isn't supported there yet, so I recommend trying using a Chromium browser.
In my case, several of the WebGPU demos on https://simplystream.com/demos fail (while keeping on falsely showing "Loading") with the error message (in DevTools):
"WebGPU requestDevice failed, trying low spec DOMException: Failed to execute 'requestDevice' on 'GPUAdapter': Required limit (64) is greater than the supported limit (32)."