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Can you get local channels such as CBS, NBC, ABC, FOX, CW (CBS+Warner Bros.), or Telemundo? These are channels that are widely available by using an over the air antenna for free. In some areas, these channels are not available unless you have a high power over the air antenna. This poses a problem for say people who live in apartments where installing a high power antenna on the roof is not possible. The only means to get access to these channels are through paid subscription services such as cable, fiber, or satellite TV. Cable cutters would love to swap out these paid services and stream.
I tried installing a few apps from the Amazon App store from Fire TV. It was a mixed bag of what is available vs what isn’t available. One thing that was consistent was that no apps provided live content for free. If the app from a major TV network offered live content on Fire TV, it was for people with paid subscription. As for what is available, you have a mixed bag. For example, the NBC app offered dateline episodes for free but America Ninja Warrior and America’s Got Talent required a sign in from a paid subscription.
A possible alternative would be to pay for Sling TV. With Sling TV, you get a handful of popular TV networks for $20/month.
Looks like it is not possible to truly cut the cord if your residence is outside the TV signal area.