I have two Google Home mini speakers that are on my IoT LAN and my trusted devices are on my private LAN. For testing purposes I currently have full two-way inter-VLAN zone forwarding between my LAN and IoT VLANs so that all devices can communicate with one another. As shown in the screenshot below I can see both speakers independently but I never see the Google Home group itself unless I put my phone onto the IoT SSID so all three devices are the same VLAN.
This problem is quite apparent on the internet with quite a few forums talking about it. See some of the links below.
There is even an article from Ubiquiti here one. Most people and article are suggesting to enable multicastDNS repeaters which I already have Avahi installed and configured with the following config:
[server] host-name=OpenWrt domain-name=lan use-ipv4=yes use-ipv6=no check-response-ttl=yes use-iff-running=no allow-interfaces=br-lan,br-iot enable-dbus=yes [wide-area] enable-wide-area=yes [publish] publish-addresses=yes publish-hinfo=yes publish-workstation=yes publish-domain=yes #publish-dns-servers=192.168.5.1 #publish-resolv-conf-dns-servers=yes [reflector] enable-reflector=yes reflect-ipv=yes [rlimits] #rlimit-as= rlimit-core=0 rlimit-data=4194304 rlimit-fsize=0 rlimit-nofile=30 rlimit-stack=4194304 rlimit-nproc=3