Well, right now their really isnt a way that I know of. You can buy Sphere 2.0 which applies soft shadows to 3D mesh, but 3DGS doesnt support light mapping for 3D models at this time. You can try using stencil shadows, but that can be a mess.

I think I have read that their is a way to bake shadows with some third party tools.

Without sphere though, I think you are out of luck.

Correct me if I'm wrong please, because I would like to know if their is a way to get shadow maps on mesh using the latest version of 3DGS.