Copied from here:
There is a persistent connection to
mtalk.google.com for push notifications, when enabled. If you don’t need that, go to settings | system | advanced | microG | Cloud Messaging | disable “receive push notifications”.
Personally, if I see value on any of the following, I’ll mention it here:
android.clients.google.com is used daily for device registration for various other services and push notifications. I went to settings | system | advanced | microG | Google device registration | disable “register device” to see if I’ll miss it. The good news are that microG strips device identifier (MAC addresses, IMEI, etc) from requests where they normally would be (and if required use random but valid identifiers instead).
- I’m blocking
google.com which are used when applications use Firebase. If my apps stop working properly, I’ll enable network access to these domains.