You are missing something. The boot process starts with the uboot from the emmc (even if ultimately booting the SD card). And coreelec changes the uboot environment of the emmc in ways that are incompatible with with the armbian code. So you need to reflash a fresh android image if you want to use armbian as that will restore the basic state that armbian is expecting.

the guide has a warning: Note: If you have previously run other distributions on the box such as coreelec the below installation will not work. You will need to restore the original android firmware before attempting the install. coreelec changes the boot environment in ways that are incompatible with these Armbian builds. I have run coreelec but only ever from an SD card, I don't think the firmware has ever been changed as if I remove the SD card it boots into the original android system. Is this likely to be true or am I again missing something.

HP Pavilion8 core processor, 32Gig RAM laptop. I wanted to limit information to limit time for digging into it, but here they are: log-build-322ed1c8-a4db-4873-85ac-be8e6a87fbd6.log.ans summary-build-322ed1c8-a4db-4873-85ac-be8e6a87fbd6.md

dig through the github actions, how the images are compiled is public information ;-)

probably time for the serial console my suspicion tells me that it will be hard to get proper logs otherwise my suspicion is that some umounts does not come back. <- try to unmount everything you can before the reboot and see if that helps.