I have this issue with an rPi4 attached directly to the hdmi port of my TV. I don't have an AVR. It's frustrating as I can't seem to get it to stay off. I have been able to power the TV off and keep it off, most of the time, if I wait for LibreElec to go to dim, before I switch HDMI to another source and then power off. I have turned off switch source in LibreElec, but I don't think that had ANY effect. Previously, I had an rPi3 with 9.2, no issues.
