Hello,
I have had this notification many times. It is a misleading warning, and I think I figured out what it is about. However, you can ignore it because AirPlay will work regardless. Airplay uses a mixture of Wi-Fi and Bluetooth and uses Multicast. They call this Bonjour.
In my case anyway, the warning is actually misleading at best, not informative at worst, caused by how it transfers information.
During the process of setting up HomePod/Apple TV, tall of your relevant account information is transferred to the device from your iPhone. Unfortunately this isn’t just including the Wi-Fi you are currently connected to, but all the Wi-Fi you do or have connected to. It Syncs this with iCloud and lets the new device know all this in case you ever need to move it somewhere and connect it to a known Wi-Fi network somewhere else. Fine, if you are taking it to your g/fs house or whatever. But when your iPhone has connected to BTWi-fi (now EE WiFi) that SSID is in your home too, along with the Wi-Fi you are already connected to.
The BT / EE public Wi-Fi doesn’t allow multicast.
The warning is therefore actually telling you that the known and trusted BT / EE network your iPhone knows about cannot use airplay. It’s not distinguishing this from the Wi-Fi you are actually on, but just on the details it’s transferring. Just doesn’t bother telling you that.
So in essence, you can ignore it.
I tested this out by ‘Forgetting’ the BT / EE network on my iPhone, waiting a good while to make sure that synced with iCloud in the background, then wiped the HomePod and restarted the process.
With the BT / EE network forgotten, the details aren’t transferred for that network and the warning never shows.
But even with the warning, as it is referring to a network you are not actually using for your home Wi-Fi, then you can ignore it and AirPlay will work regardless.
In my testing and experience anyway. I can only assume the circumstances are the same. If not, they are likely similar.
