The spying part requires a server.
If you use GrapheneOS, you can enable or disable internet access for each app.
If you use GrapheneOS, you can enable or disable internet access for each app.
This can also be done on Android with certain apps such as Netguard and PCAPDroid
(Using either a blacklist or whitelist approach)
Disabling internet access is not necessarily a hard requirement to stop this type of spying
Controlling what DNS data apps can access, if any, will usually suffice
Not sure what information you're expecting the app in question to surface if you disable internet access for it.