I'm pretty sure it's a hardware feature of specific graphic cards. Not every HDMI port has that capability and most consumer GPUs don't have it. That's why the GPU on the Steam machine is so important. It has the CEC capability out of the box.
I have a similar setup to you, but I'm running bazzite. I got around it by putting my TV (offline Hisense Roku) into a power saving mode that essentially shuts the screen off and puts it in standby. Whenever there's a change in signal, the display kicks on. However that also isn't a feature on every TV.