Hi,
despite I don't know the exact dependencies between *nix system libraries and stunnel (or if it has static libraries), have a look to the sslVersionMax and sslVersionMin options for a service level config in stunnel.conf.
As long as it works as on Windows, from the manual: "Supported versions: all, SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3"
Regards.