> And if you are a beginner, any attempt to do these exercises will invariably contain so many mistakes that they are not worth doing any more.
I totally disagree. StrongLifts (and the Starting Strength book it derives from) starts you with the empty bar. Unless you have a serious medical condition, putting 20kg on your back / chest is unlikely to result in serious bodily harm or damage to musculature. As you slowly and steadily increase the weight on the bar, you discover places where your form needs improvement. At least, that's how it worked for me (I only made it to ~100kg squats though).
Of course it's great if you can find a good coach. But I think an app like StrongLifts is a viable+reasonable substitute for a coach.