Also, for those who thought LibreELEC-RK3399.arm-10.0.4-rock-pi-4.img.gz did not boot, please try connecting the cable on the "4k HDMI" port, instead of the "2k HDMI" port. The 4K HDMI port is closer to the USB port.
I tried some 1080p and 4k videos and was glad to find hardware acceleration worked fine.
Did not try 4k HEVC 10-bit or Dolby Digital though.
This build boots fine for me:
https://archive.libreelec.tv/archive/LibreELEC-RK3399.arm-10.0.4-rock-pi-4.img.gz
However, neither the latest stable 11.0.3 of the "rock-pi-4.img" or the "rock-pi-4-plus" series work for me.
Also, the night builds 12.xx didn't work for me either:
https://test.libreelec.tv/12.0/Rockchip/
TLDR: give the 10.0.4 build a try:
https://archive.libreelec.tv/archive/LibreELEC-RK3399.arm-10.0.4-rock-pi-4.img.gz
