If you’re brave you can try importing a database dump and running foreman-rake db:migrate && foreman-rake db:seed. No guarantees and it might be good to isolate the host so it can’t reach out to the network until you’ve verified it works.
RFC: Adding Katello to a Foreman install lists some incompatibilities. The big thing to be aware of is that you can’t have nested organizations. You may need to reregister all smart proxies as well. There may also be settings in the DB that refer to the old hostname.