If you have a new discourse install the privacy policy is a staff-only topic that only an administrator can edit, to post specifically what data your site collects and how that is managed. If you need for this to be in compliance with gdpr they say best to consult with lawyers for making sure everything is correct. The public can read what is posted for that by going first to the drop down menu to the “about” and “frequently asked questions” pages which can also be edited by administrators. Here at Meta they have this link go to a different page with their policies: