PatWie
Eigen 5.0 next door
From the diff I don't directly see a benefit/issue/drawback of upgrading Eigen.
Do you have any specific new feature/Bugfix in mind?
See https://gitlab.com/libeigen/eigen/-/issues/2907
And here draft release notes of 5.0 (previous 3.5.0)
https://gist.github.com/SteveBronder/aa19ff60c02ac02de9399d056f730da6
All is ok without changes for used code here.
3.4.1 and 5.0.0 are now available since 2025-09-10. There are some breaking changes in 5.0.0 and many bugfixes, which often backported in 3.4.1. https://gitlab.com/libeigen/eigen/-/releases/5.0.0
So you are the expert of your code to check for changes or new possilities.
So perhaps 5.0.0 is not compatible and this is also an information.