Use right version of Eigen3 with Cmake - c++

Question

I want to use Eigen unsupported modulde NNLS, but in my default version Eigen 3.4.0 I do not have that file, so I downloaded the latest version Eigen 3.4.90 and I installed it using -DCMAKE_PREFIX_PATH=/home/path/to/my/prefix.
To build my project I use Cmake, and my simplified CMakeLists.txt is:
cmake_minimum_required(VERSION 3.16.0)
project(my_project VERSION 0.1.0)
find_package(Eigen3 3.4.90 REQUIRED NO_MODULE)
set(SOURCE_FILES main.cpp)
add_executable(my_project ${SOURCE_FILES})
target_link_libraries(my_project PUBLIC
Eigen3::Eigen
)
To check that Cmake found the right version, I checked the variable ${Eigen3_DIR} and I got: /home/path/to/my/prefix/share/eigen3/cmake.
However, I've been unable to use version 3.4.90. Whenever I include
#include <eigen3/unsupported/Eigen/NNLS>
the compiler (gcc 11.3.0) says that such directory does not exist, and when I write something like
#include <eigen3/Eigen/Dense>
VScode sends me to the file in usr/include, that is, it detects version 3.4.0.
How can I use the latest version?
OS: Ubuntu 22.04
One option is to replace version 3.4.0 by 3.4.90, but I do not know how to do it correctly. If I just make install version 3.4.90, will it delete automatically the old version?
On the other hand, if in the future I want to keep an old version, I want to learn how to do that.

Answer 1

I found a solution (and my rookie mistake). I oversimplified the problem to post it here.
I was using eigen3 in my library
My_project/
|- CMakeLists.txt(*)
|- main.cpp
|- lib/
|- CMakeLists.txt(**)
|- my_lib.h
|- my_lib.cpp
I used find_package in CMakeLists.txt(*), but I was including it in my_lib.h. I did so because it worked with gnuplot-iostream and sigpack, so I did the same. Now I have
# CMakeLists.txt(**)
find_package(Eigen3 3.4.90 REQUIRED NO_MODULE)
add_library(MyLib
my_lib.cpp
)
target_link_libraries(MyLib PUBLIC
Eigen3::Eigen
)
Now, I have both versions and when I ask VSCode "go to definition", it sends me to the right version.
To include the file NNLS I type
#include <unsupported/Eigen/NNLS>
However, it does not find
#include <eigen3/unsupported/Eigen/NNLS>
The project compiles now fine and it seems that NNLS works right (learning and testing).
Now I wonder why the previous method did not work.