How can I remove Gnome Desktop Environment without messing Unity DE? (Ubuntu 16.04)

To be honest it would be better to back up for files and all config files in the Home folder and do a fresh install of Ubunutu.

If not try this:

Start by running this command:

Uninstall just ubuntu-gnome-desktop

sudo apt-get remove ubuntu-gnome-desktop
sudo apt-get remove gnome-shell 

This will remove just the ubuntu-gnome-desktop package itself.

Uninstall ubuntu-gnome-desktop and it's dependencies

sudo apt-get remove --auto-remove ubuntu-gnome-desktop

This will remove the ubuntu-gnome-desktop package and any other dependant packages which are no longer needed.

Purging your config/data too

If you also want to delete your local/config files for ubuntu-gnome-desktop then this will work.

Caution! Purged config/data can not be restored by reinstalling the package.

sudo apt-get purge ubuntu-gnome-desktop

Or similarly, like this ubuntu-gnome-desktop

sudo apt-get purge --auto-remove ubuntu-gnome-desktop

Then run:

sudo apt-get autoremove 

to remove extra packages and dependencies no longer needed on your system.

You might (or might not, depending on if gdm was removed already) need to use these commands to change your login screen back to Unity's default (which is lightDM) run

sudo dpkg-reconfigure gdm

Hit enter at the prompt and then select lightdm from the options. After that you can remove gdm with

sudo apt-get remove gdm  

Finally run:

sudo apt-get install ubuntu-desktop
sudo apt-get install unity

INFO HERE and HERE

You can see all Gnome package list by :

apt list --installed | grep gnome

then remove your arbitary package by :

apt-get remove <package name>

or remove all packages by:

sudo apt-get remove $(apt list --installed "gnome*" 2>/dev/null | awk -F'/' 'NR>1{print $1}')

I also like the user interface of Unity desktop environment, so try these beautiful steps...

Step 1 : This will remove all gnome related things.

sudo apt-get remove nautilus nautilus-* gnome-power-manager gnome-screensaver gnome-termina* gnome-pane* gnome-applet* gnome-bluetooth gnome-desktop* gnome-sessio* gnome-user* gnome-shell-common zeitgeist-core libzeitgeist* gnome-control-center gnome-screenshot gnome* && sudo apt-get autoremove

Step 2 : This will remove all snap applications, if you don't do this step then you will see that there are 2 same apps some app (like 2 system-monitors, 2 terminals, 2 calculators etc) after installing unity. so run bellow code without any worry.

sudo apt autoremove --purge snapd

Step 3 : Now connect your system to a WI-FI to install Unity .

sudo apt install ubuntu-unity-desktop

Step 4 : After successful installation, reboot your system. You may have a problem that tap to click not working after replacing Gnome with Unity. If so then run below code to solve that problem..

sudo apt install xserver-xorg-input-synaptics

Now reboot your system and Login again.