Upgraded my OpenVPN client from 2.6.19 to 2.7.0, and until now I didn’t notice any problems running this version against “IPFire 2.29 (x86_64) - Core-Update 197” running OpenVPN 2.6.14.
Just wanted to let you know so anyone else who wants to upgrade has some positive feedback already 
same here openvpn-client 2.7.0 working with core update 199
cannot say the same for openvpn3-client however, but on this small system thats not presently a concern.
regards
BB
That is because OpenVPN3 aand OpenVPN Connect (mobile) clients were developed by OpenVPN for connecting to their commercial product OpenVPN Access Server and the server and the client config requirements don’t 100% match with their OpenVPN Community Server, which is the one that is used in IPFire.
OpenVPN say that these clients are compatible with various Open Source VPN servers including the Community version but only if, for instance, you don’t use the pkcs12 container that was used in earlier versions of IPFire and can still be downloaded if required or don’t use the OTP options etc that are used in IPFire.
There are various existing clients which do work with the OpenVPN Community Server in IPFire, such as Network Manager, OpenVPN for Android, Tunnelblick etc.
If you want to use OpenVPN Connect on Android or iOS then you will need to remove the existing OTP related commands that are laced in the client config by manually editing the file before importing it into your client.
Search in the forum for OpenVPN Connect and you should be able to find some previous threads on the topic.