АЛ
отрубаем сам gdm: sudo systemctl disable gdm
создаем новый юнит: sudo редактор /etc/systemd/system/newgdm.service , туда пихаем:
[Unit]
Description=kostil
After=getty@tty1.service
Requires=getty@tty1.service
[Service]
ExecStart=gdm && killall gdm
[Install]
WantedBy=multi-user.target