I have setup the xfinity remote to be compatible with my Samsung TV but it still does not provide everything so that the Samsung remote is not needed. In particular the "Home" key on Samsung remote cannot be found on the xfinity remote. So if I receive a popup from Samsung SmartThings app (Ring doorbell video, for example) I then have to use the samsung remote to navigate, respond and process the popup. Seems like the xfinity remote could make use of the some simple key combinations to emulate the "Home", "Right", "Left", "Down", "Up" and "Return" keys on the Samsung remote. If that were true then I could put the Samsung remote into a drawer and never need it again.
When it comes to Samsung UHD (smart) tv's, do not set up the Comcast remote to control anything on the tv. The same for using the Samsung remote to control the Comcast equipment.
Use the tv's remote for any functions used there. TV's broadband apps, OTA, etc. Use Comcast remote for cable channels and X1 apps. I have had no problens since 1015 by following this advice.