Linux Shout published a tutorial about installing the GNOME desktop environment on an Ubuntu Linux 20.04 or 18.04 server.
How to install GNOME desktop on Ubuntu 20.04/18.04 linux server
If you are using the Ubuntu 20.04/18.04 LTS server without a Desktop environment then install Gnome desktop GUI with these commands
How to install GNOME desktop on Ubuntu 20.04/18.04 linux server