Scrutix has no account and no sign-up. It sends no notifications. Your grid in progress and your count of completed grids are stored on your phone and nowhere else.
The fifteen dictionaries are inside the app. Scrutix plays in airplane mode, in a waiting room or on holiday. Today's grid is made on the phone from the date: no server sends it.
The network is used for two things: the ads, served by Google AdMob, and the purchase that removes them, through Google Play. In Europe, a consent form asks your choice before any ad. If you refuse, Scrutix requests no ads. You can change your choice in Settings, under Ad privacy options.
The details are in the privacy policy.