Made a Canvas, added Image, stretched. It turned out well, only covers all objects outside the canvas. I rearranged the values in Canvas Renderer Screen Space Camera - I got a great background. But the UI buttons are now also in the background. And now everything that is not on the canvas is in the foreground.
The question is how to divide Canvas elements in such a way that some of them are further from the viewer than objects outside the canvas, and which are in the foreground, Screen Overlay?