Hi there,
I have successfully enabled CDC ACM Serial Recovery mode on the nRF5340, which allows me to update the application and network core with two separate .bin files contained within the dfu_application.zip. I believe this is called non-simultaneous DFU.
I achieved this by following the relevant samples at https://github.com/hellesvik-nordic/samples_for_nrf_connect_sdk/tree/main/bootloader_samples/serial_recovery.
Eg. with the below values in the application prj.conf, and the serial recovery specific configuration values in the mcuboot.conf.
CONFIG_BOOTLOADER_MCUBOOT=y CONFIG_NRF53_UPGRADE_NETWORK_CORE=y CONFIG_ADD_MCUBOOT_MEDIATE_SIM_FLASH_DTS=y