VTK wheels for Python 3.6 and 3.7 will not available with next VTK release, support for 3.12 is being added

Development
1

As outlined in the following post, VTK wheels for Python 3.6 and 3.7 will not be available in future release of VTK.

This means that the upcoming VTK 9.3 release will include Python wheels supporting Python 3.8 to Python 3.12

See Python 3.6 and 3.7 EOL - #2 by ben.boeckel - Development - VTK