I was looking for a way to unwrap the planets into a UV/equirectangular projection so I could use them with a 3D object. Were you successful in unwrapping? Would love to know.
Yeah I think its possible to basically go the other way with how the math interprets the coords on the 2d object and project to a plane. ie It is possible to unwrap. I can post some godot code snippets or a paste bin or two if you'd like. (edit: atleast thats what I recall being able to do but its been a min since i've worked on the project.)
And sorry for the slow reply, I've been busy cooking on another project.