OK, got it. I’ve installed the snapshot app, and I can see that I can stretch out (horizontally or vertically) the live image. However, when I take a photo, it is taken correctly.
So my question is: is the live image (i.e. what is presented on screen before a photo is taken) stretched out, or is it the photo created? If the former, than it can be resized by dragging the margins. Of course, you will not know what exactly the original (non-stretched) layout is.
Maybe there is a reason why Fedora ships currently with the (legacy gtk3) Cheese app, instead of the new Camera app.