You are correct. The SoC supposed to have a way to generate composite signal, according to the scarce data I found, but I didn't manage to force the board to do

You are correct. The SoC supposed to have a way to generate composite signal, according to the scarce data I found, but I didn't manage to force the board to do so. LVDS is (presumably) working, but I don't have any compatible LCD panels lying around.