I've never seen a modem/router be useful for this. But if you have good WiFi then all you need is a WiFi Ethernet client that will receive the WiFi and provide Ethernet for the Ooma. I'll supply 1 example. Since I do run your network I can't tell if there are router changes required.
Look at devices like https://www.amazon.com/dp/B005N6XBDO
If your WiFi is not solid, this won't be either.
Please bear with me as I have no idea what I'm doing-which is why I'm here. I realize that this question may need to be moved
I just relocated to a new cabin in a rural, wooded area in which my cabin is one of 4 in a bit of a communal setting. I'm using a cell phone at the moment-completely undependable-and would like to set up my Ooma phone but as the router is not right here I don't know how to proceed, or if I even can. The internet is set up via a business class application whereby the main house has the router which is able to work for the other homes.
I have no place to run an ethernet cable from the Ooma device. There must be a way to do it but I'm simply pathetic when it comes to this stuff. Some time ago, in order to avoid Comcast's fees, I bought a modem/router and wondered if I could use a splitter to connect it to a small device that is connected to the one cable (coaxial) entering the house that is plugged in and splits off to the TV so we can get Comcast programming. And then run something to my router, lol, and the run an ethernet from the router to the Ooma box. Wow, I'm confused too. But my router would, in effect, become a relay.
Or is there a simple way PLEASE? Thanks for any help