I have created a bootable SD card with excellent instruction from
(debian-9.3-minimal-armhf-2017-12-09 image with 4.14.15-armv7-lpae-x3 kernel).
It has booted on my A20-OLinuXino-MICRO with no problem.
I have found a couple of issues, however. These issues do not appear with original Olimex image (that has some other issues, however)…
There no power in USB connector. The devices plugged into externally-powered USB hub, connected to the board are perfectly visible. Is there any way to enable the USB power on boot?
No kernel modules load by default. No sound, no power controller… Is it a bug or a feature?