Thank you for your answer Jochen,
Now working also with the latest library version :-)
Following your confirmation "NEST does not actually specify a specific library version" I restarted a completely fresh installation removing not only the build directory for the sources but also any nest related file in my ~/.local installation directory. After now compilation and installation all tests pass now and pynest can be imported.
I suppose there was and interference with preexisting files and paths. Clean build directory wasn't enough and deep clean in installation folder sokved it.
Thank you for the fantastic work and support.
Sincerely
Samuel Bottani University Paris Descartes, Biomedical Faculty