Debian 9: Install KDE for desktop environment

The following command will install KDE.

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

You can select other desktop environment.

KDE is displayed.

The following command will uninstall KDE.

$ sudo apt remove -y task-kde-desktop kde-* libkde*
$ sudo apt autoremove -y
$ sudo apt install --reinstall -y gdm3
$ sudo reboot