you have to get a custom ROM, like lineageOS. The OS itself (and most of the stock apps) are calling home to Google constantly, depending on the phone manufactu

you have to get a custom ROM, like lineageOS. The OS itself (and most of the stock apps) are calling home to Google constantly, depending on the phone manufacturer, it's likely calling home to them all the time too. You can use something like Netguard to get some idea of what's going off your device (if you're rooted AFWall). It's not perfect, but it's essential software in my opinion. You can see somethings that of that get through Netguard on PiHole, if you have it setup on your network. Removal of play services is one step, but pretty much every app on the phone from the stock keyboard ("Gboard") to all pre-installed apps call home. In the newer versions of Android, Gboard and other apps will complain every few seconds if/when Play Services is Disabled, as they don't get to send the telemetry and usage data to Google.