I am doing some research in whole home wifi and since I am leaning towards the Deco system, I am wonder why do they not come with more then two ports?

We have Voice Over Ip phone which means we have a convertor like box connected to the router, so that one port there if I need something else connected I have about 6 more ports I can use.  The Deco (and many other so it seems) have the one port to connect to the cable box (converting the cable to the RJ plug) the internet comming into the house and the other to, going from my reseach, to Backhaul to anther node  or direct connect to the other node, can this port be used to connect my VOIP home phones???

is there another device aviable to gain more ports, could I connect more old router (currently in use) to gain some extra ports without screwing around to much to get it to work??