The dealer software shows a connection tab that is missing in HE. You'll need a dealer to help with the rest of the connections unless you're able to replicate the reserved DHCP addresses from the previous router. It's good practice to make yourself a list of DHCP reserved addresses. Need a hand? Don't hesitate to PM me.
I have an account with Annex4 and have access to all their drivers. I was in contact with support for a driver issue a bit over a month ago so they are still around.
If the RPI has an audio path to your matrix while using the kodi lite driver, it will show up as a device on the navigators. So instead of programming a zone to turn on, you could select one manually and add desired zones. I'm not sure if this is the way you want the integration to work.
Simply putting Kodi (eg OSMC) on a RPI also has an option to enable or disable airplay. You could get the chowmain kodi lite driver and program a room to turn on when audio starts playing. I think that could work too. The kodi lite driver has a trial option so it could be tested before buying.