VTK Reame references build.md -- does not exist
I found this problem while reading the instructions from the top-level README.md file.
The section Building has a link to the file build.md https://gitlab.kitware.com/vtk/vtk/-/blob/master/Documentation/dev/build.md#building-vtk
This destination file does not exist.
I did find Documentation/dev/build_windows_vs.md
which is great for Windows. It appears the top level build.md file is missing, as well as Linux based build instructions (granted they are probably fairly similar to Windows build instructions thanks to the glory of CMake).