Solution for By-Passing Xfinity Fiber-Optic Modem/Router

I don't get it, you have fiber optic internet and want to convert to ethernet? Ethernet not 100% galvanic isolation, so you're going to noisier setup. Certainly, there are varying performance levels of optical, but if I started with optical I'd be seeking to optimize that rather than convert to ethernet. Not saying ethernet is bad but you're already well on your way to nice optical network with fiber optic service.

The fiber optic cable comes into my house with a SC UPC connection on the end.  My DAC will not allow me to hook up directly and I need some means of getting it in the system.  My options are ethernet or WiFi?

Uptone etheregen is one option, although only available used at present because of chip shortages. You could go with network switch with optical in capability. You could also remain optical up to  Sonore OpticalRendu. I assume your using usb in on dac?

In order to be of real help, need to know your present network setup in audio system and dac

I don't understand the problem.  Doesn't the gateway have Ethernet connectors on the inside?

I am currently using ethernet from the Xfinity gateway/modem.  I am looking to receive a cleaner signal.  I heard of some high end systems that have done this.