iOS has APIs for VPNs and “content blockers”. But as far as I know, such a filter has no access to know which process/application is trying to make a connection

iOS has APIs for VPNs and “content blockers”. But as far as I know, such a filter has no access to know which process/application is trying to make a connection. Little Snitch on macOS has to install code into kernel space. (Or at least it used to; I have not reinstalled in a long time.) The Android app you link to seems to have the functionality I think should exist as a built-in. It needs to be built-in so that non-geeks can use it. Just as users are asked the first time an application attempts to use the microphone and are able to prevent it before it starts, they should be able to limit network access and revoke it at any time. (I don’t think users should be necessarily be forced to approve Internet access for every app install. Just make it possible to revoke in the global Settings widget and encourage users to think about personal data and Internet access being mutually exclusive.)