How to fit camera to any screen size?

Very simply, I need my game to be stretched to fit most mobile screens. When I Build and Run on my android device, I can’t see part of the left and right screen because it isn’t fitted to the screen.

I’ve tried the code posted by siddharth3322 (best answer) here:

But it still doesn’t fit my screen. I’ve also looked into Canvas (since it has a Component with an option to Fit to screen) but I don’t get how it works, seems to be for UI objects only according to tutorials; and even if I try using for all objets, it spawns northeast of my scene and I can’t move it. Can someone please help me with the simplest solution to this problem?

Text instructions how to deal with this problem: