I know that there is no official support by Armbian, but as it seems several others have got it working somehow. The info for that is scattered all over, so I was hoping someone could point me in the right direction.
I didn't know about Manjaro on such a box, but I'm having a look over there right now.
Nevertheless, if any more (recent/complete) info about Armbian on such a S905X3 box should be available, please let me know.