Disable per-user seen state (\Seen flag)

Looking at /etc/univention/templates/files/etc/dovecot/conf.d/10-mail.conf I see that per-user seen state is enabled for the shared namespace.

We would like to remove this option and have shared emails with a global seen state, not per user. Searching online, Public Mailboxes — Dovecot documentation sounds like I need to remove :INDEXPVT= from the location line. However, the univention template has 2 ucr settings nested in this part of the location:

control = "" if configRegistry.is_true("mail/dovecot/mailbox/share_keywords", True) else ":CONTROL=~/Maildir/shared/%%u"
index = "/var/lib/dovecot/index/%Ld/%Ln" if configRegistry.is_true("mail/dovecot/location/separate_index", False) else "~/Maildir"
print("  location = maildir:%%%%h/Maildir:INDEXPVT=%s/shared/%%%%u%s" % (index, control))

This is univention 5.0, dovecot
mail/dovecot/location/separate_index = no
mail/dovecot/mailbox/share_keywords = yes

the resulting part of doveconf is:

namespace {
  disabled = no
  hidden = no
  ignore_on_failure = no
  inbox = no
  list = children
  location = maildir:%%h/Maildir:INDEXPVT=~/Maildir/shared/%%u
  order = 0
  prefix = shared/%%u/
  separator = /
  subscriptions = no
  type = shared

Can someone please tell me how to safely turn off per-user seen state?