I’ve been exporting GLB files with Blender but I don’t think they include KTX compressed textures for the GPU. Can anyone shed some light on this? Is it possible to include PVRTC, DXT, ASTC, ETC versions of the texture in the GLB file?
The GLTF group is heavily working on supporting compressed textures with basis
Here is the current draft: https://github.com/KhronosGroup/glTF/pull/1612
I would recommend you to export it as gltf and convert its textures to compressed textures, as a workaround. Cheers!