Just purchased a brand new Q80T and it has the exact same problem. Turning off the TV will turn off the receiver ( Denon AVR-S960H ), but turning on the TV does not turn on the receiver.
Its a shame to see this issue has been on going for over a year now.
My experience - Apple TV (ATV) connected by HDMI to a 2020 Q70T. When I first bought the TV, it was able to turn on the ATV no problem when I turned the TV on and switched to the ATV input. Every time.
Recently, this stopped working - the Q70T will no longer turn on the ATV, and when the HDMI connection to the ATV times out, the Q70T offers to turn it on with a selection on the screen using the remote, which seems to work. So, it offered to do the power on step separately. This means the TV appears to have the capability. I never had to do this before. This seemed to happen after the ATV was updated to tvOS14.
There has been talk that Apple updated the CEC such that now it won't power on with a CEC signal, and Samsung needs to update their CEC support.
Yes, CEC is a standard. But standards change and have versions.
Hi all I stumbled across this thread when my TV stopped turning my new Sony DH790 receiver on. It's turns off just fine when I turn off the TV. Well it started working ok again after I toggled the cec control off and on the Samsung TV it's a q6 from 2019 with the lasted firmware. That's the only thing I tried. It was quite annoying and I had resigned myself to it not working but seems ok for the moment. Cheers