It is possible to rotate the skybox with Ctrl+Left Button around the Y-axis. But when I enable ray tracing the position of the skybox turns back to its origin and the rotation with Ctrl+Left Button isn’t possible any more. Is this expected behaviour or bug?
There is a solution for that. See under “Ray Traced Rendering” options → “Environment North” and “Environment East”. You have to change the direction vector to rotate the Skybox image.