Wifi can easily do 20m with decent equipment. With a directional antenna can go a surprising distance, ie many KM, if there isn’t a physical barrier.
I have some unifi APs and my garage openers keep connecting to the AP at the opposite side of my house about 25m away through a few walls (including one cinder block wall). I have one unifi AP in wireless bridge mode that goes 20m-25m (what the openers are supposed to be connecting to), which has its own IP that could be pinged.
For non-ethernet/wifi solutions, there are loRaWAN based power meters/monitors/switches, but you may have to diy one of you are looking to keep costs down.
Usually wifi and wired are different manufacturers, so have very different MACs. More likely this is 2ports on the same Ethernet chip, one for wan and one connecting on the internal switch.