Tech support is a joke for sure. I only know what I know about all of this mess through research and experiment with a multitude of devices over many years. If only those on the customer support line were required to do even half as much, things would be better for sure.
For those with only a TV as a streamer or those with a soundbar or new mini receiver with only a single ARC/eARC port, various devices will have to be connected directly to a TV and good luck with it all. This would also be the case for those with new 4K capable TVs with streamers or game consoles connected to older HD receivers.
There is no standard for the feature set of HDMI-CEC in a Smart TV or even a rule about what to call it from manufacturer to manufacturer. There is no rule for the number or kinds of devices supported by a Smart TV.
There is also no standard for the allowed control by a Smart TV of devices using HDMI-CEC and every single disc player, streamer, game console, PC and cable box/tuner/DVR has its own specific HDMI-CEC feature set.
I once had nine HDMI connected devices in my system using HDMI-CEC with three devices connected to the TV and six devices connected to the AVR. It was a nightmare to configure and maintain and I had to throw in the towel.
But, to be fair, manufacturers are not entirely to blame as some folks want things to “just work” without any effort at all in learning how to make it all work. I’m sure I’ve not said “Read the f#%kin’ manual!” for the last time.
Modern processors and receivers are little marvels. It is a shame so many dismiss them for various reasons and go with soundbars and wireless(except for the f#%kin’ power cord) speakers.