Stream xfinity on Apple TV from non-xfinity internet provider?

[Edit: Grammar]
@TMPL thank you for brining us your great question about Apple TV and the awesome Xfinity Stream app! Our amazing community is here to help you find the answer. 

Here is a helpful article that goes over frequently asked questions about Apple TV and the Xfinity Stream app Xfinity Stream App on Apple TV Devices Frequently Asked Questions. In the article the answer to your question can be found.

To access the Xfinity Stream app on your Apple TV you do need to be an Xfinity Internet customer and connected to your in-home Xfinity network. 

This is from the article:
     "Can I use the Xfinity Stream app when my Apple TV isn’t connected  to my Xfinity in-home WiFi?

     No, because the Xfinity Stream app lets you access your Xfinity TV  services, which are only available through your in-home Xfinity      network. You won’t be able to use the app if you’re connected to another network, including Xfinity WiFi hotspots or any "XFINITYwifi" network that may be  available in your home. If you’re an Xfinity On Campus customer, you  must  be on your campus WiFi network."

Here is another great article that goes over the Xfinity Stream app and Apple TV: Xfinity Stream App on Apple TV Devices Overview. This article goes over set up of the Xfinity Stream app on Apple TV devices as well as has great links to information on Xfinity Stream App Minimum System Requirements. 

The Xfinity Stream app works on any Apple TV device that supports tvOS version 15 or later, including:

• Apple TV 4K (2021)
• Apple TV 4K (2017)
• Apple TV HD (2015)

I hope this information was helpful. Let me know if you have any further questions.

That someone else has commented on this prompts me to make a response that I intended to make 2 months ago but got distracted from doing.  You write "the Xfinity Stream app lets you access your Xfinity TV  services, ***which are only available through your in-home Xfinity network***."  (emphasis added.) The highlighted part of that is clearly false. With the Xfinity set-top box I can access all my Xfinity TV services and I do not have an Xfinity network (they come through the cable to my house, of course.)  With the Xfinity streaming app on my iPhone, or using the web equivalent, I can also access the streaming (internet) version of almost all of my xfinity TV channels, the exception being a few local ones that appear to have some strange agreement with Comcast, so it also false that they can only be accessed in streaming form via a home Xfinity network. I am pretty sure the Xfinity app for the Apple TV box is essentially the same as the app for the iPhone, (the underlying IOS from Apple for both are essentially the same) except that it has been deliberately crippled to insist that any streamed channels must come through an Xfinity home network.  It would take very little effort to remove that crippling (I imagine just a handful of keystrokes), and not doing so continues to give Xfinity a black eye in the view of its customers.  It certainly doesn't encourage me to switch my source of internet from my land-line carrier to Xfinity — were I to switch, I almost certainly would switch to Verizon or some other cellular provider -- who are now offering very favorable packages for home internet over cellular -- and not to xfinity internet.