update to the last test Generic image LibreELEC-Generic.x86_64-9.80-nightly-20201215-8a6ca28.img and still no luck regarding HDMI-CEC and shutdown/reboot issue.
Did some investigation to be able to trace the issue the best I can and obtain the following result:
LibreELEC:~ # cec-client -l
libCEC version: 4.0.7, compiled on 2020-12-15 03:47:30 by [email protected] on Linux 4.15.0-118-generic (x86_64), features: P8_USB, DRM, P8_detect, randr
Found devices: NONE
It seems that libCEC is a default service but it doesn't recognize the PN50 HDMI-CEC "driver"? Similar to pulse8 driver?