To anyone familiar with the MiSTeR project (De10 Nano), the RGB-Pi, Pi2Scart and many others knows that most of those commercial SFF boards are capable of 240p 15khz.
I believe the Odroid N2 is not different unless it has imposed limitations on it’s HDMI IC.
What I often do with Batocera (x86/x64) is to add NTSC 480i resolution and edit xrinitc and add
xrandr -display :0.0 --newmode "NTSC-DVD-60i" 13.514 720 736 800 858 480 484 492 525 Interlace
this becomes 480i for the main interface and crt switchres from retroarch will do the rest.
Now, without X11 this becomes a pickle.
I’m wondering if an alternative exists that can be used and if in that case, crt switchres might work.