Historically the surfboard has been the go to option for Comcast. I can’t say what the current best option is, but if you purchased your own modem in the previo

Historically the surfboard has been the go to option for Comcast. I can’t say what the current best option is, but if you purchased your own modem in the previous decade chances are you bought a surfboard. IIRC Comcast has a page of third party modems that are compatible.