Debian Base (3.10.102 BSP 2) won't boot without monitor

[Scion]

but if there is no working Debian base image to use

Choose the one based on legacy kernel now: http://www.armbian.com/pine64/  (SSH is active, wait a minute, then first login with root/1234, afterwards you're forced to change the password and create a normal user)

The one basing on kernel 4.7.0 works but is a bit slow and especially the Ethernet driver is WiP (I'm just in this moment testing new version v4 but on a H3 board running 4.8-rc6). In case you really want to give mainline a try I fear you have to read through the appropriate thread in Armbian forum.

I will give it a try.