It will be great if there is a way to restore a backup without reconfiguring the Discourse from the beginning.
For now, the differents steps to restore a backup from a server to another are :
1 - make a backup
2 - reinstall Discourse with
./discourse-setup and complete the questions : host, smtp, port etc
3 - configure SSL
4 - load the backup
Why should I complete the step 2 (and 3) if all the data are replace by the backup two minutes laters.
discourse-setup script have an option where a backup is passed in parameter to direclty install the Docker and Discourse regarding the backup variables (host, smtp etc)