Hello,
VTK 9 now has script parsing capabilities enabled by the ExprTK engine. The entire ExprTK library consists of a single .h file. As such, object files compiled from code including it tend to have a large number of symbols. Compiling in debug mode tend to exceed the maximum number of symbols, hence the error.
One solution to that is to build VTK in debug mode enabling optimization options in CMAKE_CXX_FLAGS_DEBUG, starting with -O1 and increasing to -O2, -O3, etc. until you get it right. Optimization flags decrease the number of symbols in the resulting object file.
take care,
Paulo