I too encounter the error on my Pinebook Pro when attempting to run Armbian / on eMMC (/boot files on SD card). The machine locks after this screen:
https://www.dropbox.com/s/4x7u5si8ifmw9en/Armbian_UUID_Does_Not_Exist.jpg?dl=0
Also, even though Armbian will boot off an SD card exclusively, it will not boot when eMMC is disabled (via hardware switch on the PBP). This indicates that the U-boot on the SD card image does not work.
After flashing PCM720's U-boot files to the SD card, the SD card WILL boot with my eMMC memory disabled but still encounters the above initramfs error (can't find UUID).
When run from the SD card (/boot and / files on SD card), Armbian works with both my eMMC and NVMe memory so memory support is obviously in the kernel.
