I've been trying to get rspamd working with maddy but it doesn't seem to be learning from mails I previously sent to the junk folder.
I would like to verify that the following is the correct config:

msgpipeline local_routing {
    # Insert handling for special-purpose local domains here.
    # e.g.
    # destination lists.example.org {
    # deliver_to lmtp tcp://127.0.0.1:8024
    # }

    check {
        rspamd
    }

    destination postmaster $(local_domains) {
        modify {
            replace_rcpt &local_rewrites
        }

        deliver_to &local_mailboxes
    }

    default_destination {
        reject 550 5.1.1 "User doesn't exist"
    }
}

smtp tcp://0.0.0.0:25 {
    limits {
        # Up to 20 msgs/sec across max. 10 SMTP connections.
        all rate 20 1s
        all concurrency 10
    }

    dmarc yes
    check {
        require_mx_record
        dkim
        spf
    }

    source $(local_domains) {
        reject 501 5.1.8 "Use Submission for outgoing SMTP"
    }
    default_source {
        destination postmaster $(local_domains) {
            deliver_to &local_routing
        }
        default_destination {
            reject 550 5.1.1 "User doesn't exist"
        }
    }
}

This is the maddy.conf file I use. Would rspamd work if I used a different config?

Probably you missed my reply on IRC. Currently, there is no integration to learn marked messages as spam. rspamd will use its fixed policy to detect spam.

You can probably write a script using maddyctl and rspamc and run it periodically, but that's it.