I searched again today and found this:
https://wiki.libreelec.tv/configuration/pulseaudio
And I found that just by entering the command “pactl load-module module-udev-detect” into my SSH, it works ! I can hear on my AV Receiver the music from my phone !
So this is the right way. The problem that I have is that as soon as I move in the menus on CoreELEC, the streaming breaks, and no longer works (that’s probably because of the menu sounds). and if I try to execute the command again, it says that the module failed to load. The only way is a full restart of the Odroid.
There is definitely bugs, but “pactl” is where my solution is.