But when Firebase gets that network/IP change report, what information does it get? Because if it only gets the public IP address, the reported IP will still be the VPN one, not the real one, right? So, if that were the only information reported to Firebase, wouldn’t you still be protected? Does Firebase block requests when you’re using a VPN (this could be detected, for example, if certain aspects of the network have changed but the IP hasn’t)? Is that what you mean with not getting push notifications when simulating a local IP with filters?

PS: From my research, the WiFi’s SSID can also be used to track someone’s whereabouts, but depending on where you are and how many networks have used the same SSID, it may work work well or badly. You can see that by going to https://wigle.net/ (which is a database on WiFi networks with some publicly-available information), go to the map, type in the SSID field, and click “Filter”. I’m not sure if Firebase gets that info in the network reports, but I find it likely that it does.