I did install Libreelec LibreELEC-RPi4.arm-9.1.001.img on Rasp4. I did set passthrough but I dit get HD Audio streaming. No way. Just DTS and DD. I thought Raspi 4 is able to do this.
HDMI is connected to Denon AVR. With Odroid C2 never a problem.
My first test also shows these problems:
the device is very hot. I did install two headsink
Are there any Kodi tricks to get passthrough for Atmos/DTS-HD