Use the --external-app flag to generate package for external applications (for example, updates for third-party applications).
This is only available for updates that contain an application and no SoftDevice or bootloader. Setting this option instructs the receiving device that the update should be stored, but not activated, and then passed on to a third party.
For a usage example, see Generating a package for external applications.
Note
This functionality is experimental in the nRF5 SDK and is not used in any examples.