GoT does not work anymore on Firefox/Linux

I am using Firefox on Linux to access the game. Since today, it is not working anymore with the message, that I need Windows or Mac.

It would be good to know the reason of this - it always worked well on Linux, and I can't imagine a real reason to ban users with this platform. It would be great if it would work again on Linux. Or is there another way or another browser to make it work in Linux?