You can try this code:
viewport_handle = omni.kit.viewport_legacy.get_viewport_interface()
viewport_handle.get_viewport_window().set_active_camera(str(camera_path))
You can try this code:
viewport_handle = omni.kit.viewport_legacy.get_viewport_interface()
viewport_handle.get_viewport_window().set_active_camera(str(camera_path))