New install convert from Maildir to mbox

SYSTEM INFORMATION
OS type and version Rocky Linux 8.x
Webmin version 1.999-2
Virtualmin version gpl 7.0
Related packages Postfix, Dovecot

Not found a configuration panel where to set this.
Tried changing manually postifx and dovecot config.
If I try a simple df | mail user it always end to /home/user/Maildir/new/ folder in maildir format.

Postfix: home_mailbox = Mailbox
Dovecot: mail_location = mbox:~/:INBOX=/var/mail/%u

Seems to be ignored.
Any hints?
Thanks, P.

Postfix is not the delivery agent, and should not be configured to deliver mail to local mailboxes.

How did you install Virtualmin?

procmail-wrapper should be the delivery agent (well, it wraps procmail, which is the delivery agent). We need to figure out why it didn’t get setup correctly…were there any error during installation?

Proxmox RockyLinux LXC container template
basic config
Updated it

Virtualmin install:
wget https://raw.githubusercontent.com/virtualmin/virtualmin-install/master/virtualmin-install.sh
./virtualmin-install.sh

From install.log I have only (usual in CT in my experience):
[2022/08/21 17:45:18] [INFO] - Configuring Quotas
[2022/08/21 17:45:18] [WARN] - Non-fatal error

and before (initial install stage), I had some not stopping errors rows that I think aren’t :interesting for me but may be for developers:

2022-08-21 17:40:22 URL:https://software.virtualmin.com/vm/7/rpm/virtualmin-gpl-release.noarch.rpm [18879/18879] → “virtualmin-gpl-release.noarch.rpm” [1]
Downloading Virtualmin 7 release package: Success.
error: package is not installed
Spin pid is: 1523
warning: virtualmin-gpl-release.noarch.rpm: Header V4 RSA/SHA256 Signature, key ID b9a0b8b7: NOKEY
error: can’t create transaction lock on /var/lib/rpm/.rpm.lock (Resource temporarily unavailable)
error: /etc/pki/rpm-gpg/RPM-GPG-KEY-webmin: key 1 import failed.
error: can’t create transaction lock on /var/lib/rpm/.rpm.lock (Resource temporarily unavailable)
error: /etc/pki/rpm-gpg/RPM-GPG-KEY-virtualmin-7: key 1 import failed.
Installing Virtualmin 7 release package: Success.

Anyway, back to the delivery question: after inserting the post, I remembered the procmail role in this and remembered similar situation in old server (CentOS 6.x).
Editing /etc/procmailrc I can have mail delivered to /var/mail/$USER:

LOGFILE=/var/log/procmail.log
TRAP=/etc/webmin/virtual-server/procmail-logger.pl
###ORGMAIL=$HOME/Maildir/
###DEFAULT=$HOME/Maildir/
DROPPRIVS=yes
:0
$DEFAULT

This seems to solve this part of the problem.
Is this the right way?
Anything else I have to consider?

Thanks, P.