On 15-Aug-2024 NASA 3D Resources released a 3D model of the Lunar gateway in the glTF (.glb) format along with a near Moon environment surround. See https://nasa3d.arc.nasa.gov/detail/gateway
The glTF model can be loaded into Second Life by rezzing a cube, scaling it to 1m x 1m x 1m and rotating it X = 90°, and then while its selected using Develop -> GLTF -> Open on the .glb model. You may need to move the model high in the sky (say above 1,000m) so that the ground and sea are not visible.
Creating the HDRI Environment
The “Low Lunar Orbit.jpg” image provided by NASA (here) can be converted in a suitable graphics program (e.g. GIMP) to export it as file type .exr which provides an HDRI environment. This can be loaded into the Second Life viewer as the replacement environment at present with Develop -> Render Tests -> HDRI Preview. The image below provides a link to a 360° snapshot taken in Second Life (opens on Flickr)
More on Lunar Gateway
More information on the Lunar Gateway at https://www.nasa.gov/mission/gateway/