In a Marketplace thread titled ‘Merge two Discourse forums into one,’ Mr.X_Mr.X seeks to merge two large Discourse instances — one active (60K users, 500K posts) and one offline (200K users, 1M posts) — with potential future merges of phpBB and SMF instances, possibly in milestones. Budget is negotiable, and urgency is high (‘ASAP’). itsbhanusharma offers help via PM. jericson shares experience using a documented method to move categories and topics between Discourse instances, noting it works well for users and posts but requires automation and time for large datasets. pfaffman also offers assistance via PM. The thread underscores the complexity of large-scale forum migrations and the need for automation and careful planning. A warning note reminds users to exercise due diligence when engaging contractors.
If you just need the users and their posts, this works really well. The trick would be to automate the process. Also, it would take a long time for thousands of posts and users!