In my house we have computers in two rooms at the opposite sides of the house. My computer has the router (from Xfinity) and my wife's computer is in a room about 35 feet away that we use for an office. Between the two computers is a wall that contains a fireplace. We've had this setup for several years without any problems but in recent times my wife has been doing a lot of Zooming and we've noticed that when the office door is closed that she frequently gets dropped from Zoom sessions. I know next to nothing about this type of thing but would a WiFi extender help? If so can you suggest a good one that would be compatible with the Xfinity router? Assume that cost is not a factor. If you don't think the extender would help can you suggest anything else?
Some tips for improving WiFi performance;
http://corporate.comcast.com/comcast-voices/10-ways-you-might-be-killing-your-home-wi-fi-signal
https://www.xfinity.com/support/articles/improve-your-wireless-home-network
There are other options. Google for WiFi repeaters / range extenders, WiFi mesh systems / pods, powerline ethernet adapters, MoCA adapters. Good luck !
I have found much variation of wi-fi Zoom stability based on location within the home, and of course, plug in a wire and ALL the problems go away. (So that's the way I do it now.)
As far as I can see, video conferencing is more picky about wi-fi than anything else. If this is a single level home over a basement or crawspace, I would run an ethernet wire. Just changing the angle a bit so the fireplace is not directly in-line might help too. If you're not video conferencing, maybe swap positions (of you or the router.)