I used this manual https://support.plesk.com/hc/en-us/articles/12377563936023-How-to-disable-IPv6-addresses-on-a-Plesk-server to disable ipv6 on debian 12.
But had a problem with dovecot have add
to /etc/dovecot/dovecot.conf
listen = *
So will dovecot work.
By default maps non existing...