Dang! No wonder I didn't get past the blank screen after the "Starting kernel" message (over HDMI).
The OPI Ubuntu image works, with a bug in HDMI (out) to DVI-D (monitor input) though: messed up the colours.
I can take a look at the what folks at OPI did. Am neither a graphics expert, nor do I have a USB-TTL cable though. So I'll go slow about it. I already checked out https://docs.armbian.com/Developer-Guide_Build-Preparation/. Is there someone on this forum who can help me if I get stuck somewhere?
Newbie alert; this is my first Pi board and am new to the forum as well.