Just in case you didn't know, Windows 10 offers a
3D Builder app that you can download and install
for free from Microsoft Store.
Among other things, 3D Builder can import and automatically repair (!)
glTF files, and export them to a few common 3D formats including
OBJ. SketchFab's glTFs often come broken, i.e. not fully compliant with the MS glTF format specs. You can also repair them manually (if you know how to), and view them, in the MS
Visual Studio Code editor equipped with the corresponding plugin, but you can't export them from VS Code to other 3D formats.
Below please find an SCV model converted directly in my 3D Builder from a repaired
scene.glTF file downloadable from SketchFab. It is not 100% perfect and it still needs Y,Z swapping. But it is a much better starting point for modding than your own MAT file that was apparently developed from scratch.
