Just came across this news report https://www.techdirt.com/articles/20200225/14150743985/smithsonian-releases-28-million-images-3d-models-into-public-domain.shtml about the Smithsonian Institution making a whole bunch of stuff available for free download and reuse under a Creative Commons CC0 licence.

More info on their home page https://www.si.edu/OpenAccess.

I had a quick look at one or two 3D models from https://3d.si.edu/cc0, and I see OBJ, glTF (OpenGL Transfer Format) and GLB (binary version of glTF) options available. These are all open formats, well-supported in non-proprietary software.