Planethoster doesn't officially support configuring their VPN on Ubuntu Linux. It's possible that configuring L2TP over IPSec worked with Ubuntu 14.04, but it definitely didn't work by Ubuntu 16.04. I found a solution today, and now L2TP over IPSec works on Ubuntu 17.04, see https://ingbrief.wordpress.com/2017/10/14/ubuntu-l2tp-vpn/ . Unfortunately, I haven't been able to get L2TP over IPSec to work with Kubuntu 17.04. I've reported this at https://bugs.kde.org/show_bug.cgi?id=385745 . This also seems to be a problem with Deepin Linux, so I've reported that as well, see http://feedback.deepin.org/feedback/detail/8109 . There might be a workaround to put the advanced Phase1 and Phase2 Algorithms in manually, but I don't know how to do that!