With Ubuntu 18.04 Canonical introduced new network management called Netplan. In nutshell Netplan allows to directly configure network and/or switch between two network configuration daemons networkd and NetworkManager. By default networkd is configured for Ubuntu Server and NetworkManager for Ubuntu Desktop.

Go to   /etc/netplan/01-netcfg.yaml configuration file and change it:

FROM:

TO:

apply changes by executing:

$ sudo netplan apply

sudo apt-get install ubuntu-desktop