To install Gnome Session:
sudo apt install gnome-session.
To enable touchpad Tap-click after Gnome session installation:
vaidas@vaidas-SATELLITE-L855:~$ gsettings get org.gnome.desktop.peripherals.touchpad tap-to-click
false
vaidas@vaidas-SATELLITE-L855:~$ gsettings set org.gnome.desktop.peripherals.touchpad tap-to-click true
vaidas@vaidas-SATELLITE-L855:~$
More information: https://itsfoss.com/enable-tap-to-click-on-ubuntu-login-screen/