Disabling Extra Tty

When I boot my system, I have 6 tty (agetty). I want to keep tt1 and disable the other ones, ie tty[2-5]. How to disable all tty but tt1?

My system is a Ubuntu 18.04 which I customized to be lighter. I feel that I followed all answers from Ask Ubuntu without success. What I have done already: Following How can I reduce the number of TTYs? I changed in /etc/default/console-setup

ACTIVE_CONSOLES="/dev/tty[1-6]"

in

ACTIVE_CONSOLES="/dev/tty1"

and deleted /etc/init/tty[2-5].conf.

Inspired by How do I increase the number of TTY consoles?, in /etc/systemd/logind.conf, I have set

NAutoVTs=1
ReserveVT=1

I is worth to mention that I don't have systemd-logind.

Despite those changes, after reboot, I have 6 agetty.

Here the full output of systemctl status

    State: degraded
     Jobs: 0 queued
   Failed: 7 units
    Since: Thu 2020-04-16 16:50:49 CEST; 1h 31min left
   CGroup: /
           ├─init.scope
           │ └─1 /sbin/init
           └─system.slice
             ├─irqbalance.service
             │ └─921 /usr/sbin/irqbalance --foreground
             ├─systemd-udevd.service
             │ └─440 /lib/systemd/systemd-udevd
             ├─systemd-journald.service
             │ └─429 /lib/systemd/systemd-journald
             ├─ssh.service
             │ ├─1116 /usr/sbin/sshd -D
             │ ├─1158 sshd: clement [priv]
             │ ├─1318 sshd: clement@pts/0
             │ ├─1319 -zsh
             │ ├─1419 sudo systemctl status
             │ ├─1420 systemctl status
             │ └─1421 pager
             ├─
             │ └─1019 /sbin/wpa_supplicant -s -B -P /run/wpa_supplicant.wlan0.pid -i wlan0 -D nl80211,wext -C /run/wpa_supplicant
             ├─lvm2-lvmetad.service
             │ └─433 /sbin/lvmetad -f
             ├─system-getty.slice
             │ ├─
             │ │ └─1110 /sbin/agetty -o -p -- \u --noclear tty6 linux
             │ ├─
             │ │ └─1111 /sbin/agetty -o -p -- \u --noclear tty1 linux
             │ ├─
             │ │ └─1113 /sbin/agetty -o -p -- \u --noclear tty3 linux
             │ ├─
             │ │ └─1109 /sbin/agetty -o -p -- \u --noclear tty5 linux
             │ ├─
             │ │ └─1108 /sbin/agetty -o -p -- \u --noclear tty2 linux
             │ └─
             │   └─1112 /sbin/agetty -o -p -- \u --noclear tty4 linux
             └─smartd.service
               └─919 /usr/sbin/smartd -n