The opt-out functionality is made available for apps via methods in our SDK explained in this documentation: https://developers.piano.io/analytics/data-collection/how-to-send-events/consent/
When the app is launched, you will simply need to give the user the option to opt-out via a dedicated screen. If the user doesn't wish to be tracked, you can then set the consent mode opt-out in the tag to prevent the creation of a client ID (we will instead receive "opt-out").