You can use a network state to change the skybox in a Session. Each Toggle Skybox script can load a single skybox material, and then toggle that skybox on and off.
Component overview
The Network State Trigger_Toggle Skybox component has a single parameter for the skybox material that you want to load. For information about how to create a skybox material, refer to Using skyboxes in the Unity documentation.
Network State Trigger_Toggle Skybox component
The following diagram shows an example of how to arrange the components in Unity, and the required references.
Example use of network states to synchronize toggling a skybox change
