At downloads in spectra eigen 3.4.0 is for download.
Eigen 3.4.1 is a update to 3.4.0, only with bugfix of 65 issues.
https://gitlab.com/libeigen/eigen/-/releases/3.4.1
Eigen 5.0.0 is a greater update with significant changes of 274 issues..
https://gitlab.com/libeigen/eigen/-/releases/5.0.0
5.0.1 Bugfix in
https://gitlab.com/libeigen/eigen/-/releases/5.0.1
Perhaps all is ok in communication to actual spectra.
Perhaps some changes are here necessary to eigen 5.0.0.
C++ 14 is here full supported, but this will end in next version.
C++ 17 is full supported in main branch at version 5.0.0.
Next version of eigen will support only c++ 17 or higher.