Please rebuild openvpn package against supported libraries
The openvpn package is currently built against LibreSSL.
OpenVPN tell you quite clearly that this is not supported, e.g.:
“Please note that LibreSSL is not a supported crypto backend. We accept
patches and we do test on OpenBSD 6.0 which comes with LibreSSL, but if
newer versions of LibreSSL break API compatibility we do not take
responsibility to fix that.”
https://openvpn.net/index.php/open-source/downloads.html
and elsewhere on their website where they describe dependencies and state OpenSSL or PolarSSL.
Surely you are just asking for trouble by building against unsupported libraries ?
(from redmine: issue id 9325, created on 2018-08-22)