If you have coax in your home, and you aren’t using it for cable TV and/or Internet, you can use it as a substitute for Ethernet (and get better results than Wi-Fi or Powerline). Solid Signal has started selling these, which support Gigabit and are backward compatible with the older-generation DECA adapters. I replaced two of my older-generation adapters (one at my main switch, and one in my bedroom) with the new gigabit model. I had DirecTV years ago, so I was already set up for DECA (all of the runs connect to a multiswitch). The coax for my Internet (Comcast) is totally separate from the old DIrecTV wiring.
If you have coax but are using it for cable and/or Internet, you’ll need MoCA adapters. You could also run a separate point-to-point drop and use DECA instead (you can use splitters for more drops).
If you want to use DECA but don’t need gigabit, the older-generation adapters are cheap.