As others have mentioned, TLS 1.3 is not yet supported. But a little bit of context for that decision as of early last year. https://github.com/libressl-portab

As others have mentioned, TLS 1.3 is not yet supported. But a little bit of context for that decision as of early last year. https://github.com/libressl-portable/portable/issues/228#issuecomment-375916733 https://github.com/libressl-portable/portable/issues/228#iss... We will support 1.3 once the standard is firmed up and finalized (i.e. ceases to be coopted by vendors making changes to allow for people to continue to run moribund middle boxes that can't recognize a new protocol on the wire) Since there is effectively nothing wrong with TLS 1.2 with a sanely chosen cipher suite today, we believe a clean careful implementation is more beneficial than early adoption. So there's no rush on the part of the developers to support it. Skimming the commits on that git mirror we can see 1.3 related commits started hitting late last year.