vtk PyPI only has versions >8.0.0. Is there a place where I can get vtk==7.1? I tried pip install vtk==7.1 only to run in to:
Collecting vtk==7.1
ERROR: Could not find a version that satisfies the requirement vtk==7.1 (from versions: 8.1.0, 8.1.1, 8.1.2)
ERROR: No matching distribution found for vtk==7.1
My impression is that it will be a nontrivial amount of work to construct a pip-installable package for VTK 7. You can start by looking at how it was performed for VTK 8 and VTK 9. Alternatively, you may want to consider moving to VTK 9.