Last week was a bad week so I've been inactive. I turned Hex 3D years old and I'm sorry, I've been very sick. Right now I'm in a 73dF room wearing a sweat shirt and insulated hoody and still I'm chilled.
I have much I could write about booting on the small ARM boards but have not the energy. Just remember that Linux has drivers to see eMMC (not NAND) storage as a hard drive volume. As such If you boot Linux on that board you should be able to flash EB NG to it the same as an sd card. The H3 ALWAYS tries first to boot from sd card then tries eMMC/NAND 2nd. So there is a possibility that it would work. It shouldn't hurt to try it anyway.
Armbian has a Multitool program that can back-up eMMC/NAND storage to an image and flash to it from an image. You might investigate that. It is mentioned a lot in the Armbian on TV Box forums.
I'll try to be back soon as I mend.