Hello @user_1,
Sadly the delta updates are not compatible with your configuration.
rootfs-image updates are exclusively with Operating Systems where we integrated Mender with the bootloader. For example, a yocto-based OS that has Mender layer included or a Debian/Ubuntu-based system that uses GRUB or u-boot. In the case of Jetson Linux (Ubuntu-based) from Nvidia, we created an Update Module that makes usage of the official Nvidia utilities (like nvbootctrl) to handle the swap from Active to Inactive slot, and some other utilities from Nvidia in order to copy the payload into the inactive slot.
Saying that, we are not talking about a real rootfs update at block-level but using the mechanism of copying its content as Nvidia designed their process in this way.
When you deploy delta updates by using the Mender way, the read-only active slot is copied to the inactive one, and then the deltas are applied. In this case, to have the active slot as read-only is a must.
So far what I can advise is to compress the payload of the mender artifact by any other technology and then tell Mender by using an Update Module how to uncompress this payload.
Hope this information helps, have a nice day!
Luis