Nothing uses Ethernet-over-HDMI. It doesn't actually exist outside of a spec proposal. Even though in theory it'd be really cool. Imagine if your receiver could also be the network switch for all the devices. I'd actually pay money for such a thing. But, yeah, not actually a thing it turns out. So you definitely don't need to worry about your smart TV using it any time soon.
It would be super silly and probably against every spec ever written, but I’d love to be able to plug a digital signage Raspberry Pi into a TV and not need any other cables thanks to Power-over-Ethernet-over-HDMI.
on the flip side, USBC does all 3, so the future is already here!
RPi4 should support power and network through its usbc plug, however you'll still need another cable for video currently.
the frame.work "SBC" would allow all 3 through the same connector, but, you'll be looking at ~400+ per SBC just to achieve this, but the key thing is, its 100% doable if you get the hardware combination right
The RPi might not quite manage it, but any USB-C Mac and many Windows machines can. Maybe. Just make sure you know whether you're expecting to use Thunderbolt over USB-C or USB-C alt modes, and make sure you're within the power budget of a PoE -> USB-PD adapter. And I suspect you'll need to fudge the monitor power supply somehow too.
The different bits will locally need a number of wires to join them together, but you might manage to run the whole thing off a single ethernet cable.
It would be super convenient to avoid having a mess of cables and a switch behind your TV, or having to use Wi-Fi, that has its limitations, especially these days with higher and higher bitrates.
