Another aspect of this is why Apple/Google let this happen in the first place. GrapheneOS is the only mobile OS I can think of that lets you disable networking on an per-app level. Why does a period tracking app need to send data to meta (why does it even need networking access at all)? Why is there no affordance of user-level choice/control that allows users to explicitly see the exact packets of data being sent off device? It would be trival for apps to have to present a list of allowed IPs/hostnames, and users to consent/not otherwise the app is not allowed on the play store.

Simply put, it should not be possible to simply send arbitrary data without some sort of user consent/control, and to me, this is where the GDPR has utterly failed. I hope one day users are given a legal right to control what data is sent off their device to a remote server with serious consequences for non-compliance.

"GrapheneOS is the only mobile OS I can think of that lets you disable networking on a per-app level."

Don't need to "root" mobile phone and install GrapheneOS. Netguard app blocks connections on a per-app basis. It generally works.

But having to take these measures, i.e., installing GrapheneOS or Netguard (plus Nebulo, etc.), is why "mobile OS" all suck. People call them "corporate OS" because the OS is not under the control of the computer owner, it is controlled by a corporation. Even GrapheneOS depends on Google's Android OS, relies on Google hardware, makes default remote connections to a mothership that happen without any user input (just like any corporate OS), and uses a Chromium-based default browser. If one is concerned about being tracked, perhaps it is best to avoid these corporate, mobile OS.

It is easy to control remote connections on a non-corporate, non-mobile OS where the user can compile the OS from source on a modestly resourced computer. The computer user can edit the source and make whatever changes they want. For example, I use one where, after compilation from source, everything is disabled by default (this is not Linux). The user must choose whether to create and enable network interfaces for remote connectivity.

> Why does a period tracking app need to send data to meta (why does it even need networking access at all)?

In case you want to sync between multiple devices, networking is the least hassle way.

> Why is there no affordance of user-level choice/control that allows users to explicitly see the exact packets of data being sent off device? It would be trival for apps to have to present a list of allowed IPs/hostnames, and users to consent/not otherwise the app is not allowed on the play store.

I don't know that it ends up being useful, because wherever the data is sent to can also send the data further on.