Convert a .X mesh to a modern format I have a bunch of meshes in the .X format, which isn't supported by many 3D applications today. Therefore, I would like to convert these to a modern format like fbx or gltf/glb. 

Since these meshes are proprietary, an offline solution would be preferred. What would be an ideal way to achieve this lossless-ly?
Blender appears to have a .X importer.  It's a plugin that ships with Blender, but is disabled by default, so you have to enable it in User Preferences.  See: https://blender.stackexchange.com/a/8749/18161

Blender also has a glTF exporter.  For now that's a separate download, from here: glTF-Blender-Exporter