L2TP-IPSec for Ubuntu 16+

sudo apt install intltool libtool network-manager-dev libnm-util-dev libnm-glib-dev libnm-glib-vpn-dev libnm-gtk-dev libnm-dev libnma-dev ppp-dev libdbus-glib-1-dev libsecret-1-dev libgtk-3-dev libglib2.0-dev xl2tpd strongswan

git clone https://github.com/nm-l2tp/network-manager-l2tp.git
cd network-manager-l2tp
autoreconf -fi
intltoolize

./configure --disable-static --prefix=/usr --sysconfdir=/etc --libdir=/usr/lib/x86_64-linux-gnu --libexecdir=/usr/lib/NetworkManager --localstatedir=/var --with-pppd-plugin-dir=/usr/lib/pppd/2.4.7

make
sudo make install

sudo apparmor_parser -R /etc/apparmor.d/usr.lib.ipsec.charon
sudo ln -s /etc/apparmor.d/usr.lib.ipsec.charon /etc/apparmor.d/disable/
sudo apparmor_parser -R /etc/apparmor.d/usr.lib.ipsec.stroke
sudo ln -s /etc/apparmor.d/usr.lib.ipsec.stroke /etc/apparmor.d/disable/

sudo apt remove xl2tpd  
sudo apt install libpcap0.8-dev
wget https://github.com/xelerance/xl2tpd/archive/v1.3.8.tar.gz
tar xvzf v1.3.8.tar.gz
cd xl2tpd-1.3.8
make
sudo make install