Ethernet source

NEW routers have faster wifi, 5G, if yours is old, ask for a new fast one, with wifi and 4 ethernet output jacks.

ethernet cable from cable co. router is without doubt the best for anything. I would poke thru the wall.

Is that cable company device in the garage wifi? Close enough for a good signal? You could try wifi from it before you poke thru the wall, 

You can buy a network switch, it will have 1 input for ethernet cable from cable company router, the switch will have wifi and 4 output jacks.

i.e. I put a wired switch near my home theater, then 4 separate ethernet cables to: TV; AVR; BluRay; PC and use it's wifi for strong signal in that area for tablet/laptop: reaches living room, porch, back yard.

“I could poke thru the wall and install an outlet fairly easily.”

@russellrcncom
That would be the most effective way to get ‘wired’ and noise free signal to your ultrarendu. I would steer clear of ‘audiophile’ network switch or hubs. The multiple LAN ports in these switches are prime source of noise. All of these network devices generate noise from the equipment itself along with noise from the AC adapter of the power supply.

Well, I just tried using a wifi repeater and noticed no improvement (or degradation) of sound quality.  Next step is a phone call to Verizon.  It probably wouldn't hurt to switch out the modem As it's almost 9 years old.  At the same time I,m going to talk to them about activating the Ethernet port on the controller.