I to would like to know. I had both going just fine, then all of a sudden the 2.4 stopped brodcasting. So my Ring Doorbell 2 stopped working. When i logged into the router, it will not let you rename or anything with the channels other than disabling one or the other. i tried that and still no go. i was able to change the setting of the router through the xfinity website and split the channels but the router will not brodcast the 2.4 so nothing will contect to it. I tried the reserved ip address tips from xfinity but nothing shows up. the router has to brodcast the 2.4 or nothing will connect to it.
If you're using a leased Comcast gateway you should probably just trade it in for a free replacement or upgrade. Contact your local Xfinity store, call (800) XFINITY or use the Xfinity Chat assistant. If you prefer to deal with it in this thread, let me know and I'll have a Comcast rep assist you.