Ok, so i had some time to do more tests...
Well, in first place i kinda feel a bit stupid regarding the HDMI issue... Actually it was the cable that was not correctly connected...
After diagnosing that issue, i tried to boot the image that i created again, but it seems that the board skips the boot from the sdcard and boots directly to the Android system which is still installed on the EMMC.
I then tried @rafman image (Armbian-unofficial_24.11.0-trunk_X96q-v5-1_bookworm_current_6.6.44_mate_desktop.img.xz), and the board boots correctly (with no UART console messages. Is it supposed, or might i have a problem in my UART?)
For all the tests i did i used USBImager, so i am excluding problems with the card flashing method.
Is anyone else creating the images from Armbian main branch?
Thanks