OpenVPN has to be migrated to the new server.
Old server: Ubuntu 14.04.5, easy-rsa 2.0, OpenVPN 2.3.2
New server: Ubuntu 20.04, easy-rsa 3.1, OpenVPN 2.4.7
After copying "/etc/openvpn" it did not work, server log was not written and client log says "Unknown error" (see below)
I suppose...