​​​​​​
Gosh, someone actually trying to do the right thing, separating their devices and IoT stuff, bonjour gateways, I doff my cap STS-134 . But in trying to do the right thing, you run into the nonsense of non-enterprise networking where it's a lottery just how much thought anyone makes of implementing their network stacks to consider multicast properly, especially VPN vendors. Even in the enterprise network space where you're paying big bucks this is really difficult to get consistent results, and consistent support for handling multicast in software based networking (like VPNs), my experience is that consideration of multicast usually has a lower priority than IPv6. YMMV.