Shader fallbacks as of the newest update (1554) only fallback _MainTex, where previous version of VRChat supported:

_Color

_MainTex

_Glossiness

_GlossMapScale

_SmoothnessTextureChannel

_Metallic

_MetallicGlossMap

_BumbMap

_OcclusionMap

Shader effected: Standard, Standard (Specular Setup), Autodesk Interactive, Standard Lite, and any custom shaders that use the same shader properties.