WebXR crashes in Safari 15 (due to xrCompatible WebGL context flag)

First of all, thanks for Safari 15! We however would like to report a rather critical issue experinced by some Verge3D users both on iOS and macOS (see for example this forum topic). As one can guess, it is relevant to other WebGL engines/libraries as well.

It appears that the xrCompatible flag that is usually employeed for initializing WebGL context (to allow for WebXR) is broken. Normally, the browser should just ignore unsupported flags. However, it causes Safari 15 to crash on WebGL/WebXR content. All worked well before this Safari update.

Hope this can be fixed soon! Thanks