Comment 5 for bug 1689833

> My guess is that systemd starts OpenVPN too early before the network is brought
> up sufficiently. Running 'sudo systemctl edit --full openvpn' and adding
> 'Wants=network-online.target' does not change that behaviour.

I tried this to test:
[Unit]
(...)
After=syslog.target network-online.target
Wants=network-online.target

It then worked. Can you give that a shot?

Upstream adopted a mixed approach and split the services into a server and client part, and adopted different after/wants values for each (see https://github.com/OpenVPN/openvpn/commit/28bd79ac980488dbfce2e8136287e38c6f35a043)

I don't think we can take an approach as the above for a stable release update, though.