Using the latest master and the aforementioned Unity version, attempting to generate Lightmap UVs creates islands that are miniscule and have far more padding than the specified texel amount. This ...
Follow-up to #668. Unity's ModelImporter replaces UV2 when "Generate Lightmap UVs" is selected in the importer, UnityGLTF currently just uses the underlying Unwrapping.GenerateSecondaryUVSet() method, ...