I just bought a Pi4 2GB yesterday, installed your 9.80 devel image (above), and tested playback of a few H.265/HEVC 1080p DTS HD Master Audio files. Everything worked great. I also tested playback of H.264 1080p files (none with HD audio) and those played back fine as well.
Thank you to anyone/everyone who worked to get HD audio on the Pi 4 working!
Since your post was from July, I tested out the latest Pi 4 release build of Libreelec, but this does not appear to have HD audio enabled.
On a semi-related note, I copied over the Sox command line player binary from another Pi 4, and this is also working fine. I am currently playing back a 24 bit / 96 KHz FLAC file, and I wanted to see if the Pi was outputting the audio at 16 bit 96 KHz (as it does in Raspbian) or 24 bit 96 KHz. Normally I would cat /proc/asound/card0/pcm0p/sub0/hw_params to check, but w/ Libreelec I get:
rate: 96000 (96000/1)
This confirms the rate is 96 KHz, but I'm used to the format looking like "S16_LE" (or S24_LE, S32_LE) to see the bit depth.
Is there any way to check the bit depth on the Pi 4 w/ the audio driver used by libreelec (vc4-hdmi?)
Thank you again!