In this guide, you will find out how to fix the D3D12 error in Gotham Knights.
First, you have to open Steam and then click on the library tab at the top of your screen. In the library, you have to find Gotham Knights, then right-click on it, and go to properties. In the general tab under launch options, you have to press the space button, then input “-force-d3d11” and close it.