Yes, I did test that image with HDMI unplugged (Armbian_20.11.7_Nanopim4v2_buster_legacy_4.4.213_desktop).
Display controller is R9514 (https://is.gd/p5DKfg) and was booting fine with image flashed on eMMC (Armbian_20.11.3_Nanopim4_bionic_legacy_4.4.213_desktop)...don't have the eMMC anymore.
The image you pointed me to does not boot at all from the SD card.
NicoD's image is the only one booting on SD card as long as the HDMI cable is disconnected.
Thanks...I understand now.