RE Version of OpenSSl ?

HI Vincent.
 
You need the sources of the OpenSSL library, not the compiled library.
On Ubuntu, the packages with sources are typically named xxx-dev where
xxx is the package that provides the library. I don't have a Ubuntu
currently, but try looking for something like openssl-dev or
libopenssl-dev etc.

Thanks, the dev packege seems named libssl-dev.
But:
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$ sudo apt install libssl-dev
[sudo] Mot de passe de vincent :
Lecture des listes de paquets... Fait
Construction de l'arbre des dépendances... Fait
Lecture des informations d'état... Fait     
libssl-dev est déjà la version la plus récente (3.0.13-0ubuntu3.4).
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In english: "libssl-dev is already the most recent version (3.0.13-0ubuntu3.4).

Vincent