In TLSv1.3, client and server negotiate (EC)DHE groups. The list of (EC)DHE groups should be configurable. For OpenSSL, some details are written in below. - "Groups" section of [Using TLS1.3 With OpenSSL](https://www.openssl.org/blog/blog/2018/02/08/tlsv1.3/) - [SSL_CTX_set1_groups_list](https://www.openssl.org/docs/manmaster/man3/SSL_CTX_set1_groups_list.html)