Apparently I need to get a PPPoE username and password to be able to run my main Deco from the ONT. More to come on that process. Thanks everyone.

@yves_b "Even connected to Deco 1 by a direct Ethernet cable, Deco 2 shows as connected by wifi to Deco 1? What if you connect a computer by cable to Deco 1?" That is correct on Deco 1>Deco 2 direct...

@jzchen My provider is Brightspeed (CenturyLink/Quantum Fiber). The fiber comes into the house, plugs into a Calix GigaPoint 803G ONT, which plugs into my C4000XG modem. The modem has 4 ethernet out...

@yves_b All Deco units are connected directly to my modem via Cat6.

@yves_b I connected Deco 1 to Deco 2 via ethernet cable, with no change in connectivity. I am unable to daisy chain all 3, as I only have 1 jack at each network drop.

Been there, done that. No dice. According to TP-Links guide/article: "When the Deco is configured in Access Point mode, you can wire satellite Deco nodes to any Deco unit, or the main modem/router."...