GrapheneOS has a built in network "Kill Switch" for each app individually on your phone.
As soon as a app is installed it you are prompted to grant network access to the app, you can also choose to restrict it after the fact as well.
There are also some other apps on Android that do the same that I have come across, but I have gotten pretty used to what GrapheneOS offers me now built in.
This is useful for restricting network access for keyboard, galary, game, or emulator apps for example.