No EIGEN3_FOUND setted after find_package(Eigen3)

The ceres-solver will not work because when it calls find_package(Eigen3), no EIGEN3_FOUND will be setted, so it believes no eigen library is founded. But I test using 'apt install libeigen3-dev' in ubuntu20.04 will works because the Eigen3Config.cmake set the EIGEN3_FOUND.