Your TV has a coax S/PDIF output, not TOSLINK? That's unusual.

If so, yeah, you can use an RCA cable. I'd make sure it's something decent and not the garbage cables that come with a lot of devices. Something like this is cheap and would work great: https://www.amazon.com/Monoprice-Wall-Rated-Digital-Coaxial/dp/B002EA9438/.