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.
Back when I used Comcast ten years ago, that was the one that I had that I used with them. I mentioned it because I'm 100% certain it can be used. There are a million others too.
Edit: thanks for the downvote! The few I clicked on their website have weak ratings but they are rated much better on Amazon.