Created because of the inventor's dislike of going to the gym, lying on the floor, or doing arbitrary movements disconnected from anything else in life.
You can train a lot of muscles if all you have are free weights + bench. Simply search, "Home workouts Dr. Mike" on YouTube.
It’s mostly dumbbell focused, so needs much less space than a barbell. That specific model brings its own screen, but you can get a smaller unit that just holds weights and uses your iPhone depth camera.
I follow their programs plus I select workouts that follow upper/lower/rest pattern. Maybe it’s less optimal than 5x5 but I’m getting great results regardless - so far down 4” at my waist and feeling a lot better; as the OP mentioned my back pain is gone.
But you might also look into calisthenics, which is enjoying a surge in popularity, it seems. Lots of good stuff out there on bodyweight training with a variety of adapted equipment.
I’m sure there are some channels that are ok, but my cynical take is that most channels are there for one reason: to make money (by getting views).
This is often (usually?) contradictory to giving good guidance, vs. telling people what they want to hear.
https://youtu.be/x1kv3oKoZkQ?si=iehzC8H815vEtA1M
Part of the problem is that most of this works. If you pick up heavy things, you will get stronger. If you're trying to differentiate yourself you'll focus on specific techniques or sports, but really, the basics are not hard: do something that's difficult and your body will adapt to improve its ability to do that thing.
However, some specifics that I've found useful:
Barbell Medicine - focuses on strength training, not just barbells.
The Bioneer - a little lifestyle heavy, but the basic advice is sound.
Alan Thrall- also barbell focused, but lots of good advice to be gleaned there, including on bodyweight.
Ross Enamait - boxing focus, but bodyweight stuff. His book "Never Gymless" is good.
Underground Strength Gym - an oldie, but a goodie.