What image are you trying to boot from sd, Linux?
I don’t think you maybe don’t even need to erase the eMMC, i was using this guide, did it with win32 disk imager, everything went great, have a look in this thread, you’ll see a guide from rdfktv member, 3rd-Party Ubuntu ROM for Khadas VIM.
Do not use the guide on the beginning of the topic, this is what you are looking for
