Sorry, I think here introduced much confusion.
Firstly, [2] points to the legacy booting images which are delivered by Hisilicon propertied images. I checked again in the official AOSP releasing, so far we still use the legacy booting images.
[3] is equivalent to [2], but [3] uses the open sourced booting images (ARM-TF mainline code + UEFI).
Could you confirm one thing for ‘I have tried both to no avail’? Here your target is to recovery board or you have recoveried board successfully, but failed to move some folders into SD card?
If you want to enlarge the space for rootFS and get more sufficient disk size for your work, I suggest you to use the ‘data’ partition to flash the debian rootFS, and in the kernel command line you can specify to mount the ‘data’ partition as the root device. I am not sure this info is useful, maybe it’s irrelevant.