==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.6.3 MARIADB edition
- Deployed with iRedMail Easy or the downloadable installer? downloadable
- Linux/BSD distribution name and version: Debian 12
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MariaDB
- Web server (Apache or Nginx): nginx
- Manage mail accounts with iRedAdmin-Pro? no
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I know that Debian 12 isn't officially supported, but I just installed it on a barebones Debain 12 system and it is working flawlessly, so I though I'd share the minor adjustment needed to get the script installer to function.

• in /iRedMail-1.6.3/conf/global

elif [ -f /etc/debian_version ]; then
        # Debian
        export DISTRO='DEBIAN'

        echo "${DISTRO_VERSION}" | grep -E '^(10|11|12)$' &>/dev/null
        if [[ $? != 0 ]]; then
            export UNSUPPORTED_RELEASE='YES'
        fi
    else
        export UNSUPPORTED_RELEASE='YES'
    fi

• in /iRedMail-1.6.3/conf/php

elif [ X"${DISTRO}" == X'DEBIAN' -o X"${DISTRO}" == X'UBUNTU' ]; then
    if [ X"${DISTRO_CODENAME}" == X'bullseye' ]; then
        # Debian 11
        export PHP_VERSION='7.4'
    elif [ X"${DISTRO_CODENAME}" == X'focal' ]; then
        # Ubuntu 20.04
        export PHP_VERSION='7.4'
    elif [ X"${DISTRO_CODENAME}" == X'jammy' ]; then
        # Ubuntu 22.04
        export PHP_VERSION='8.1'
    elif [ X"${DISTRO_CODENAME}" == X'bookworm' ]; then
        #  Debian 12
        export PHP_VERSION='8.2'
    fi

I think that was all that I had to change for using MariaDB/RoundCube/Fail2Ban. I didn't try installing SOGo and netdata is going to require at least pulling in netcat from another package 1st (I stopped there).

Hope this saves someone else some time