@WYLDSTALLYNS Thanks. It's a Brother MFC-J875. My assumption was it could not be seen because it was on the 2.4GHz wifi. Is that not right and a new printer may in fact be able to be scene from DECO attached devices? 

I have the printer on the TMOBILE gateway 2.4GHz wifi because a legacy laptop needs to print on it. Can the DECO put out a 2.4Ghz wifi as well as operate the mesh and maybe that will work?

The 2.4ghz band should work fine, in fact I think most printers use this band. But, depending on how the device sets up it can easily be a pain depending on device’s. I’ve learned to keep my printer’s password on hand. 

Plus, the routers require apps now, which they think adds to it, but most tech people loathe the app approach.

  @WilsonLR If I understand your setup, I suggest running the Deco mesh in Access Point mode (rather than Router mode).  That would allow all local devices to communicate, as if they were all connected to the gateway.

If your legacy device cannot connect to the wifi of the Deco, it is perhaps because it does not support the security protocol (wpa...) configured on the Deco.  Indeed, the Deco should be accessible via the 2.4ghz band.

Depending on your model of Deco, you could perhaps create an additional, 'IOT" wifi network on the Deco, and configure that wifi network with lower security setting.  

  @yves_b Thank you. Next time I am onsite I will look into it. During initial setup, I don't recall seeing a way to do anything other than the standard ethernet connected "Main" Deco with satellites. You are correct about the legacy laptop. It does not support the later security protocols. It is however in range of the Deco IOT. Attached is the current topology. 

  @WilsonLR 

Good, that confirms my assumptions.

I suggest first changing the operation mode of the Deco from Router to Access Point (AP).  It is not proposed by the app during the initial setup, and it is proposed as an option by the app, under More/Advanced.  When the Deco mesh runs in AP mode, the gateway will act as DHCP server for all devices, and all devices will be able to communicate as if there were all connected to the gateway.  It is usually recommended, anyway, not to have two DHCP servers, so, regardless of the current issue, it is a good idea to run the deco in AP mode.

Once everything works, I suggest trying to activate the IOT network of the Deco, with lower security setting, and connect your legacy devices to it.  This will allow the legacy devices to connect to wifi anywhere in your house.  I suggest as well disabling the wifi of the gateway, and using only the wifi of the Deco.

I do not know how your house is wired.  Once you run the Deco mesh in AP mode, you could, if you prefer, wire the Deco 2 as well into the gateway, instead of wiring it to Deco1.  This assumes that the gateway acts as a switch, so it is not guaranteed to work.