The current supported devices are the same as the Fibe TV app and are listed at https://www.bell.ca/Fibe-Alt-TV
(click on "View compatible devices".) You may also be able use your computer by connecting an HDMI cable to your TV.
Also see "Offer details" at the bottom of the page:
Viewing with Apple TV, Amazon Fire TV Stick or other compatible devices is only available within your home and Fibe Internet with unlimited usage is required. Apple TV
: compatible 4th gen. or 4K box only. Amazon Fire TV Stick
: compatible basic edition only. Other compatible devices: Google certified Android TV
The only TVs with native support are the Sony Android TVs. You can also use the NVIDIA SHIELD TV and Xiaomi Mi Boxes which run Google certified Android TV OS (not to be confused with the cheap knock-offs that run the Android mobile version.)