Hi,
Slept on the issue a bit more research I resolved this morning.
Samsung Q80T sets have one HDMI port that is setup to receive 4k @100/120HZ @2.1GBPs 2.1. The others apparently do not (Absence by omission) and supports AMD freesync et al Link https://www.avforums.com/reviews/samsun…t-review.18207/
I plugged the cable into that port and the switching works as expected. Playing HDR content switches to HDR. When the content stops mode switches back to non-HDR mode. No other changes made to the setup. Hope my couple of posts help others troubleshoot/setup their Samsungs.
Moral of story, regardless of what the system (no fault of Libreelec) tells you the display will support check the HDMI port compatibility with your display and plug the cable into the right one. Rather than seeing it as a gaming port (as marked) which you plug your nintendo/PS4/5 into