Please use the crash reporter to send that issue in so it can be resolved. In the meantime you can try and manually adjust your ini settings so that UEFN runs in DX11 mode.
or this
This wiki gives a good explanation at how to do it but the file you’d be modifying in this case would be:
<Personal>\AppData\Local\UnrealEditorFortnite\Saved\Config\WindowsEditor\Engine.ini
Since you can’t open the editor to set the setting you’d have to change the ini. Additionally please make sure drivers are up to date and that your graphics card supports the latest dx12