I found the 'debian-8.7.1-amd64-DVD-1.iso' image here: http://cdimage.debian.org/debian-cd/current/amd64/iso-dvd/, burned it to SD card in a USB reader with Rufus https://rufus.akeo.ie/, and booted it from USB on the Udoo X86 Advanced hardware with 32GB eMMC Storage. I selected the GUI Install from the menu, and all proceeded remarkably fast and smooth without a hitch (except the WiFi, but gigabit Ethernet enabled downloading all required additional files) until the last when it came to grub. The installer advised that it had detected another OS being installed, and presented me with a few choices to which I wasn't sure of the correct one, so I took the default. That must have been wrong, as now Debian won't boot with grub from the eMMC "Hard Drive." I'm not at all familiar with grub. I can boot into recovery mode though, and from the command line it appears the install was successful. So I'm close, but don't know exactly how to proceed to make it bootable. Any clues sincerely appreciated.