yopp

Try different monitor indeed helps.
So this is my case (just have time to test it this morning) that explain the issue I met):
- in 2020 I tried a full HD Dell monitor and I can see the boot screen and logs from that monitor
- in 2023 I tried again on a 2K LG monitor and it shows nothing on screen
 
So as SteeMan said : SD card quality and  monitor type are the factor we need to check when we encounter this 'HDMI boot issue'
Cheers.

@yopp  I assume you are following these instructions: https://forum.armbian.com/topic/17106-installation-instructions-for-tv-boxes-with-amlogic-cpus
 
And you specifically are following this note: 
 
Note: If you have previously run other distributions on the box such as coreelec the below installation will not work.  You will need to restore the original android firmware before attempting the install.  coreelec changes the boot environment in ways that are incompatible with these Armbian builds.
 
If you have previously booted coreelec, armbian will not boot.