This issue seems to appear on Oculus devices (I’m using AirLink on a Quest 2). WebXR seems to fire up on Edge fine, but in Firefox 94.01 on Windows 10 Pro (now has native WebXR support) I get a “WebXR is not supported” in the Playcanvas “VR Starter Kit” demo. Mozilla Hubs, and other demos do indeed work, i.e. Hello WebXR! - Mozilla Mixed Reality