Eigen comes with a lot of `Find*.cmake` files. At least for some of these libraries, CMake provides its own scripts. (I'm guessing the Eigen versions are from times when CMake did not have these.) This means that with a modern CMake, the (probably very outdated) find scripts of Eigen shadow the built-in modules of CMake. I stumbled upon this issue when looking at BLAS, and trying to make the build use the `Imported` targets that recent CMake has, if available. For the specific case of `BLAS`, there are a total of `5` commits in the Eigen repository, whereas the `FindBlas` in cmake seems to have received quite a lot of commits alone in this year: https://github.com/Kitware/CMake/commits/master/Modules/FindBLAS.cmake Should we identify and remove the custom `Find*.cmake` scripts for all libraries that come with built-in find modules for `CMake >= 3.10`? Edit: With `LAPACK`, the script supplied with Eigen actually causes errors, whereas the cmake one correctly locates openblas.