With VTK-9.0.1 that comes default in Fedora 34, I'm getting a compilation error building vtkbool.
CMake Error at vtkbool/CMakeLists.txt:113 (include):
include could not find load file:
vtkWrapHierarchy
CMake Error at vtkbool/CMakeLists.txt:114 (vtk_wrap_hierarchy):
Unknown CMake command "vtk_wrap_hierarchy".
With VTK-9.0.1 that comes default in Fedora 34, I'm getting a compilation error building vtkbool.
It's because vtkWrapHierarchy was removed in https://github.com/Kitware/VTK/commit/8d61ac62bfb3c532d1d3506d5f7fd495e49c4295.
I'm not using the PythonWrapper. Maybe you could disable it by default in VTK 9 until this problem is fixed?