I first started out with Manjaro KDE and used it for a while before switching back to using Gnome (used Ubuntu 18.04.2 before).
However, when I first tried installing Gnome on my system, I could not remove KDE and it was a mess, and I had to reinstall the whole system.
I have installed Gnome and now I want to install XFCE.
I have searched and tried different methods. Although they suggested that I reinstall Manjaro again with the flavor I want.
But here is the recipe that worked for me.
The recipe of: Gnome to XFCE
sudo pacman -Rsn gnome gnome-extra gdm
This will remove GNOME, GNOME software and the GDM login manager leaving you with only a command line interface. You can leave GDM installed if you want to use it as a display manager. This would make it easier.
If your removed GDM also disabled it with systemctl.
sudo systemctl disable gdm
Run these commands while GNOME is not running from inside another TTY (
CTRL+ALT+F1-12). Restart the system after doing this.
sudo pacman -S xfce4 xfce4-goodies
to install XFCE4 and XFCE4 software.
If you removed GDM install and configure a display manager of your choice: https://wiki.archlinux.org/index.php/Display_manager#Graphical