Debian 9: Install LXDE for desktop environment

The following command will install LXDE.

$ sudo apt install -y expect
$ cat <<EOF | expect
set timeout -1
spawn sudo apt install -y task-lxde-desktop
expect "Default display manager: "
send "2\n"
expect eof
EOF
$ sudo reboot

You can select other desktop environment.

LXDE is displayed.

The following command will uninstall LXDE.

$ sudo apt remove -y task-lxde-desktop lxde* openbox lightdm-gtk-greeter
$ sudo apt autoremove -y
$ sudo apt install --reinstall -y gdm3