chewitt thanks again, I did some more hours of tests. I am using 0 adapters, and a certified 4k@60Hz cable by Amazon basics:
https://www.amazon.nl/dp/B07KSDB25X (from Netherlands amazon)
I finally was able to SSH into LibreELEC while connected to the TV, then I did getedid delete and getedid create, this changed my cmdline.txt to:
boot=UUID=2001-4441 disk=UUID=30f5d869-400e-4a82-8b7b-a5173e9001ba quiet console=ttyAMA10,115200 console=tty0 drm.edid_firmware=HDMI-A-1:edid/edid-HDMI-A-1.bin,HDMI-A-2:edid/edid-HDMI-A-2.bin video=HDMI-A-1:D video=HDMI-A-2:D
with the monitor it was:
boot=UUID=2001-4441 disk=UUID=30f5d869-400e-4a82-8b7b-a5173e9001ba quiet console=ttyAMA10,115200 console=tty0 drm.edid_firmware=HDMI-A-2:edid/edid-HDMI-A-2.bin video=HDMI-A-2:D
and after getedid delete it was just:
boot=UUID=2001-4441 disk=UUID=30f5d869-400e-4a82-8b7b-a5173e9001ba quiet console=ttyAMA10,115200 console=tty0
The problem is that in none of them I was able to hear audio! Do you have any idea why should be then?