Running my free trial of Fubo, and it's performing exactly the way I hoped. There's the Fubo app I can run on the Fire Stick, and I can run the regular apps I've used for years that require a cable provider to log in, because they now accept my Fubo credentials in place of the cable TV credentials.
Cable gets turned off next week. Cost of Fubo is about $45 per month, Cable was $155. I can upgrade my internet to a higher speed for about 10-20 bucks. It's fine for now, but 4K TV is coming.