I just wrote the Armbian Ubuntu Jammy Desktop image to an SD HC card and booted up fine with it (although I can only boot if I disconnect the HDMI cable -- when boot up is finished, I can plug it in and use the desktop. That's another story, but I have the same issue with official NanoPi Ubuntu images.
Next, I transferred the Armbian OS to the eMMC and indicated that I wanted both the boot and system to be on the eMMC. After transferring the rootfs and getting the Power Off prompt, I powered off, then removed the SD HC card, then attempted to boot. However, when I tried to power on again, the NanoPi went into a reboot loop. Armbian will not boot without the SD card inserted. I just get a splash screen and a few lines of text and then it cycles all over again.
I booted up again with the SD card looking at the "df" command, I can see that the OS is actually on the eMMC, but the /boot partition is still on the SD HC card. I attempted to update the bootloader with the armbian-install command -- it only gives a single option to update the bootloader on SD/eMMC (doesn't give a way to choose between those two devices). That didn't solve my booting problem. I still needed to have the SD HC card inserted too boot. Then I tried the OS transfer again and that didn't work either.
Is there a solution to this? It seems the Armbian installer just can't properly update the eMMC so that I can boot from there.