you might have to disable tracker protection for the page — godot tries to use local storage but gets blocked because it's in an iframe
Thanks for the insanely quick reply. I did some console debugging and figured out that I needed webgl.force-enabled on in about:config before I could get to the point where I'd see your indirect call to null. Will restart FF now and try one more time, if I hit a third error I'll have to wait until I have a block of serious debugging time.