Any updates on this? I am just trying to install Armbian on the eMMC of 5B. It’s not working, so I ran into this thread. If possible, I wouldn’t want to open the case (and undo the thermal tape) to access the maskrom button, so I was wondering if the you think the instructions of sns1801 could be adapted to constructing a new image with several invocations of dd? Then use any image on an SD to flash the custom image from a USB stick using dd?