Nothing builds strength, especially back strength, like lifting heavy things. If you have any space at home, a squat rack (if needed to save space, free standing on each side) and a bar with some weight. Just do something like 5x5 stronglifts app and some stretching. An hour (total, for warming up, stretching, and lifting) three times a week and your world could change for the better. Mine did. You could even do this watching nor listening to some entertainment. I had back pain. Hurt to downhill on a mountain bike. Sleeping got worse. Sitting got worse. Then I started lifting and stretching (was stretching for the cycling already, but needed some new stretches for the lifting). As long as I stretch my glutes/hip and pick up heavy things, I have no back issues. The stretching is key to keep the new muscle loose.