To migrate even a single project from Cloud to Data Center one must create a full cloud site backup and restore it on an on-prem instance of Jira. If you have team-managed/next-gen projects you will not have the ability to export until you have destroyed your team-managed projects.
Per the documentation: Jira Cloud products are regularly updated with the absolute latest features and improvements. Some of these features are incompatible between cloud and server products. Team-managed projects, for example, do not exist in Jira Server or Jira Data Center. To create a usable server backup, you need to delete all team-managed projects from your Jira Cloud site.
In other words, if you have to create a server export and you have team-managed projects, the act of export is a permanently destructive process. What can we do if we need to keep our team-managed projects intact?
