You can run 1GBps on it. There are companies that sell hardware for it, even specialized multi-port switches.

They are mostly used to retrofit the old CCTV infrastructure for newer PoE-based systems. It's typically called Ethernet-over-Coax. E.g.: https://www.nvtphybridge.com/ or https://www.dualcomm.com/collections/ethernet-over-coax/prod...