Fortnite stretched (4: 3) is no longer possible?

I played in front of a long 4: 3 1280x1024 but have verified the game and since then it does not matter how many times in gameuser setings I change it.
Ps: stop writing 4: 3 is unnecessary etc.

With Alt + Enter the game can be switched to full screen mode.

My recommendation goes into your settings of your graphics card and adjust the low resolution there and it should be stretched to full monitor size. The advantage of setting on the graphics card is that you can also use full screen in windowed mode and taboo without any problems from the game.