Packages for updating external applications can be generated by nRF Util for nRF5 SDK by setting the –external-app option.
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. The following command is an example for generating an external application update package:
nrfutil pkg generate --hw-version 52 --application-version 0x01020101 –application app.hex --key-file key.pem app_dfu_package.zip --zigbee True --zigbee-manufacturer-id 123 --zigbee-image-type 321 --zigbee-comment good-image --external-app --zigbee-ota-hw-version 231