Postfix 3.3 in Leap-15 does no longer support mysql virtual maps.

Installed is:
i  | postfix            | A fast, secure, and flexible mailer
i+ | postfix-mysql      | Postfix plugin to support MySQL maps

When I use this line in main.cf:
virtual_mailbox_maps = mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf

and restart postfix, or check postfix with postconf -n this ends up in this
warn messages:

postconf: warning: mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf: unused
parameter: password=xxxxxxx
postconf: warning: mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf: unused
parameter: dbname=postfix
postconf: warning: mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf: unused
parameter: query=SELECT maildir FROM mailbox WHERE username='%u' AND active=1
postconf: warning: mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf: unused
parameter: user=postfix
postconf: warning: mysql:/etc/postfix/mysql_virtual_mailbox_maps.cf: unused
parameter: hosts=localhost

In Leap 43.2 this was possible without any issue. Another MySQL/MariaDB Client
problem in Leap 15? Postfix manpage and sample configurations still suggest
this as a possibility.