Google Play services and Apple services provide central infrastructures for some apps. For example, push messages are sent via these services. Government agencies use this fact to monitor iPhone and Android devices.
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You can protect yourself from this by using apps that do not require Google or Apple services. Also avoid alternatives such as microG if you have installed your own operating system. For example, install apps from F-Droid that do not require these services. Messengers such as Telegram, Signal and Matrix offer their own alternatives for centralized push messages.