I created a shader tree to convert albedo/metallic/roughness outputs to Arnold standard shader inputs.
You can download the project here:
Test scene content:
a few mesh
substance (sbsar file from Substance Share)
Arnold’s color management settings:
Display Driver gamma: 1
More info about that:
I used a ramp node to convert the metallic map into an IOR map. (Please use Fresnel everywhere. This is far more accurate than reflectance at normal workflow.)
lowest value: about 1.5
highest value: 13 (silver)
Don’t forget to update your Substance plug-in.