My materials are not working neither. I've created a model with Dust3D (I think pairing Dust3D with PixelOver is a powerful combination) and in blender I'm able to see the material and texture applied ok, but in PixelOver it's all black. The model:
https://drive.google.com/drive/folders/1I5FMWqE2r3j43zJIxuBRg2p2UFjEcR26?usp=sha...
PD: Fixed! Blender was not exporting the texture, just the .obj and .mtl
Anyway I think everything will work much better when support for importing a packed format like GLTF comes.