@Jeddar - I got excited for a minute because what you described definitely sounds like it could be it, but alas when I looked the 'Wireless Multicast Forwarding was already enabled. I did find some...

I have the AX3000 router (Hardware Version: Archer AX50 v1.0) setup on a given subnet, and I want to cast to google devices (chromecast/nest speakers/etc..) on a different subnet. Research has...