@akschu If you configure the XE20 as a satellite of the XE75 (in wireless mesh mode), it will work as you want.

The two Deco will collaborate to get your ethernet stuff on the wifi network.

Wouldn't setting up the new box in satellite mode make it into another access point?  Can I disable the access point feature to ensure it's just a station-bridge?

  @akschu 

I am not sure what you mean exactly by "station bridge".

A Deco satellite node works almost like an access point, indeed.  And this is exactly what you need.

The difference between a regular Access Point and a Deco satellite, is the collaboration between the satellite Deco and the main Deco.  They will dynamically adapt their bachhaul, and will provide a seamless roaming to devices moving between the Deco. 

Actually, you could use any access point to achieve what you want.

You want to create a space where devices can communicate using their MAC addresses.

You can achieve that by combining access points and switches.  Both appliances extend the broadcast space, the LAN, or the subnet.

Bridges are useful when you have networks with different technology.

Ethernet and wifi are, from this perspective, a single technology.

Your ISP modem can sometimes act as a bridge.  Usually, it rather acts as a router.

  @yves_b 

It is not what I need, I don't want wifi clients picking this new satellite only to have the frame relayed which burns the avaiable wifi bandwidth twice.

No, I can't use any access point to achieve what I want.  The 802.11 protocol doesn't bridge well because the src mac address of the frame must be the access point, not the wired device behind it.  Read more here: https://tinyurl.com/2ms5t85m

Most access point vendors modify the protocol slightly to add the 4th mac address so that you can bridge, in the link above it's called station-bridge, but it only works when you use the same vendor for the AP and station.

The TP-link deco obviously does something like this so that you can plug ethernet hosts into the access point, but I don't know if any deco device will act like a layer 2 bridge between any other deco device, and even if it does, if I can disable the access point feature so that I'm not burning the bandwidth twice.

I guess I should have just known better and bought cambium, ubuiqiti, mikrotik, etc.  Egg is on me for buying home user wifi gear.

  @akschu I do not undertand why you refer to MikroTik.  Do you have MikroTik appliances?

  @akschu 

A mesh of Deco will transmit traffic between two devices connected on the mesh, as well as the traffic between any device and the Internet.

That is the purpose of a mesh.

nevermind.... 

  @akschu 

A Deco mesh will, collectively, act like a single Access Point or as a single Router.

An satellite Deco does not act as an individual Access Point.