PySide2 [linux]: polygons aren't shaded correctly when rendered in pyside2

System

• Linux (Arch) Kernel 5.5.2
• VTK 8.2 (anaconda)
• PySide2 5.13.2 (anaconda)

Problem:

Polygon faces aren't rendered correctly. The issue came with vtk 8.1.2 -> 8.2.0

Steps to reproduce:

• download test.py
• install vtk with pyside 2 on linux

conda install vtk=8.2 pyside2
python test.py

i tried different combinations of inverted orientation / culling,..