distro/systemd/openvpn-server@.service contains
Documentation=https://openvpn.net/community-resources/reference-manual-for-openvpn-@OPENVPN_VERSION_MAJOR@-@OPENVPN_VERSION_MINOR@/
which gets resolved at build-time to
Documentation=https://openvpn.net/community-resources/reference-manual-for-openvpn-2-7/
That website does not exist (Page not found). Guessing for 2.6 leads to
https://openvpn.net/community-resources/reference-manual-for-openvpn-2-6/
which redirects to https://openvpn.net/community-docs/community-articles/openvpn-2-6-manual.html. And https://openvpn.net/community-docs/community-articles/openvpn-2-7-manual.html does exist as well, so it's just a redirect that's missing.
distro/systemd/openvpn-server@.service contains
Documentation=https://openvpn.net/community-resources/reference-manual-for-openvpn-@OPENVPN_VERSION_MAJOR@-@OPENVPN_VERSION_MINOR@/which gets resolved at build-time to
Documentation=https://openvpn.net/community-resources/reference-manual-for-openvpn-2-7/That website does not exist (Page not found). Guessing for 2.6 leads to
https://openvpn.net/community-resources/reference-manual-for-openvpn-2-6/
which redirects to https://openvpn.net/community-docs/community-articles/openvpn-2-6-manual.html. And https://openvpn.net/community-docs/community-articles/openvpn-2-7-manual.html does exist as well, so it's just a redirect that's missing.