Ubuntu server 22.04 Postfix/Dovecot error: postfix/smtpd fatal: no SASL authentication mechanisms

Following the Ubuntu's official guide Install and configure Postfix , when I run telnet localhost 25 I get

Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Connection closed by foreign host.

When I look into the logs I get

$ sudo tail /var/log/mail.err
Dec  7 11:38:17  postfix/smtpd: fatal: no SASL authentication mechanisms

___ The above example is running in a virtual machine, but the same happens in a server in the cloud, and running telnet remotely to the domain. (I tried to replicate the process in the VM to see if I could spot what happens more easily). I've read every post, blog, article, old and new, tried every configuration I could think of, and yet the error persists. I can't figure what is wrong. My configurations: **/etc/postfix/main.cf**

# See /usr/share/postfix/main.cf.dist for a commented, more complete version


# Debian specific:  Specifying a file name will cause the first
# line of that file to be used as the name.  The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname

smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no

# appending .domain is the MUA's job.
append_dot_mydomain = no

# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h

readme_directory = no

# See http://www.postfix.org/COMPATIBILITY_README.html  -- default to 3.6 on
# fresh installs.
compatibility_level = 3.6



# TLS parameters
smtpd_tls_cert_file = /etc/ssl/certs/server.crt
smtpd_tls_key_file = /etc/ssl/private/server.key
smtpd_tls_security_level = may

smtp_tls_CApath=/etc/ssl/certs
smtp_tls_security_level = may
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache


smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
myhostname = 
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = , .local, , localhost.localdomain, localhost
relayhost =
mynetworks = 127.0.0.0/8 [::1]/128 [::ffff:127.0.0.0]/104 [::1]/128 192.168.30.0/24
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
home_mailbox = Maildir/
smtpd_sasl_type = dovecot
smtpd_sasl_path = private/auth
smtpd_sasl_local_domain =
smtpd_sasl_security_options = noanonymous,noplaintext
smtpd_sasl_tls_security_options = noanonymous
broken_sasl_auth_clients = yes
smtpd_sasl_auth_enable = yes
smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination
smtp_tls_note_starttls_offer = yes
smtpd_tls_loglevel = 4
smtpd_tls_received_header = yes

**/etc/dovecot/conf.d/10-master.conf**

service auth {
  unix_listener auth-userdb {
    #mode = 0666
    #user = 
    #group = 
  }

  # Postfix smtp-auth
  unix_listener /var/spool/postfix/private/auth {
    mode = 0660
    user = postfix
    group = postfix
  }

  # Auth process is run as this user.
  #user = $default_internal_user
}

___ The SSL files in the VM I created following the official guide Security - Certificates . In my cloud server I tried with Let's encrypt/Certbot files. I added them in the **/etc/dovecot/conf.d/10-ssl.conf** file

ssl_cert =  systemd[1] : Starting Postfix Mail Transport Agent...
dic 07 12:26:07  systemd[1] : Finished Postfix Mail Transport Agent.

**Dovecot**

● dovecot.service - Dovecot IMAP/POP3 email server
     Loaded: loaded (/lib/systemd/system/dovecot.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2023-12-07 12:26:08 UTC; 12min ago
       Docs: man:dovecot(1)
             https://doc.dovecot.org/ 
   Main PID: 3372 (dovecot)
     Status: "v2.3.16 (7e2e900c1a) running"
      Tasks: 5 (limit: 2220)
     Memory: 3.1M
        CPU: 44ms
     CGroup: /system.slice/dovecot.service
             ├─3372 /usr/sbin/dovecot -F
             ├─3373 dovecot/anvil
             ├─3374 dovecot/log
             ├─3375 dovecot/config
             └─3381 dovecot/stats

dic 07 12:26:08  systemd[1] : Starting Dovecot IMAP/POP3 email server...
dic 07 12:26:08  dovecot: master: Dovecot v2.3.16 (7e2e900c1a) starting up without any protocols (core dumps disabled)
dic 07 12:26:08  systemd[1] : Started Dovecot IMAP/POP3 email server.

___ I followed the *Troubleshooting* section in the guide. I tried many permutations, but nothing works, and the logs don't give any detail I can work with. The question is already *too long*, and as I tried so many things I prefer not to make it longer, please ask in the comments and I will edit adding relevant information if needed. Maybe I'm missing something very basic.