Substrate + .glb PBR-Material Support?

Substrate + .glb export supporting PBR-Materials:

It looks like, once you switched to Substrate Materials, you can’t carry basic PBR-Material Information over to .glb file format.

Running some tests. I was not able to export a .glb file that contains standard PBR-Material information, including standard texture maps for:

  • Diffuse
  • Roughness
  • Metallic
  • Normal

Am I missing something substantial here?
Or is it just not supported - which would be truly a real bummer!

Thx for any info on that!
cheers