Amazon.com: Motorola MG7700 Modem WiFi Router Combo with Power Boost | Approved by Comcast Xfinity, Cox and Spectrum | for Cable Plans Up to 800 Mbps | DOCSIS 3.0 + Gigabit Router : Electronics
Can't get compatible modems list from https://www.xfinity.com/support/devices/ : r/Comcast_Xfinity
Amazon.com: NETGEAR Cable Modem CM500 - Compatible with all Cable Providers incl. Xfinity, Spectrum, Cox | For Cable Plans up to 400Mbps | DOCSIS 3.0 : Electronics