Hi there, was this issue ever resolved? I am experiencing the same problem - when booting from the default eMMC I get some chinese version of android (useless, but confirms that HDMI actually works), but when booting from an SD card I can see that everything works via TTL but no HDMI. I tried all of the images available from Orange Pi website as well but none of them gives HDMI output.
Bad SD card and underpower are ruled out because TTL monitoring confirms Armbian booting up and HDMI hardware works because the useless Android works, so it is something to do with Armbian itself.