Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.86
Broken: version: 2.81 (sub 14), branch: master, commit date: 2019-10-06 14:05, hash: rB54a9649e2636
Short description of error
Just thought I'd try moving some of my commercial work over to Blender, but I seem to be having a problem where smooth shading doesn't appear to be working, most prominent with a normal map, but still visible without. Geometry appears to be OK, no sharp edges etc, normals fine, auto smooth tried on and off, made sure there's no custom split normals data etc.
I've tested the same geometry in Redshift/Houdini, and it seems to be fine.
Exact steps for others to reproduce the error
open file and press render: