Cant discover Chromecast groups

OpenWrt 23.05.0

Using avahi,smcroute and some firewall rules my Android app HiFi Cast (an excellant app by the way) can discover and play to my chromecast devices and my Denon AV across my 2 vlans.
But what it cannot do is discover the Chromecast 'Speaker Group' .
If I move the phone to my vot (vlan of things) it finds the group .
This subject has been much discussed but I have seen no fix discussed

Works as designed in a single subnet only.


Than why is my Linux Chrome Browser able to discover the 'Speaker Group' across subnets ?

It is long research from you with tcpdump, probably your mcast forward works top and browser sends mcast with default ttl like 64.

so the ttl for the Group would be different than the chromecast device ?

ttl is not address, it is how many more routings packet could pass.

I know what it is . I can fathom why it be different then the physical cc device

I think what you have to do is run tcpdump and compare with what is described in cisco guide ie what gets forwarded what does not. What you described roughly looks like what they do....