Ever since the new tvOS 13 update, my Samsung TV no longer turns off after I put the Apple TV to sleep. Under settings, remotes and devices, the option to control TVs and Receivers gives error: "You can't use System control with this configuration."

Something was broken in this update.

My Samsung QLED did not recognize the Apple TV 4K after the update.

It worked flawlessly prior to the update.

The control TV and Receivers was toggled off in the update.

I was able to toggle on, but TV still does not recognize it as an Apple TV. Unknown device is all I can get.

I did get control back though.

I had to unplug the HDMI cable, wait a few minutes, then plug it back in to get control back.

I just went to the "settings" app in the Apple TV home screen and clicked on the "remotes and Devices" tab then down to the "control TVs and Receivers" tab in the Home Theater control area and clicked on it to make sure it stated "on". It didn't taker right away so I unplugged the HDMI cable and plugged it back in. It saw there was a connection on the HDMI input for the TV but the TV didn't know what it was. I just classified it as a computer and then was able to control the Apple TV again. I am hoping in a future update whatever was changed will revert and it will identify again. Good luck with it as it doesn't seem to be a common problem.

CEC is dependent on the TV and each manufacturer has their own implementation. You can refer to your manual for troubleshooting, check for a firmware update and consult with Samsung if necessary.

That wouldn’t have been caused by the update

Ha. This worked for me too. Exact same problem. The good ol' air gap reboot.