How do I clone a project on JIRA Cloud?

[JohnI]

The link given in the answer to this question is broken, and Googling the link's title gives numerous pages like this one in which JIRA Command Line Interface is recommended.  However, the documentation states that the cloneProject action requires the Clone Plus plugin, which is not available on Cloud.  I tried it anyway, and running:

jira.sh --server SERVER --user USER --password PASSWORD --action cloneProject --project KEY --toProject NEWKEY --cloneIssues --name 'Clone'

gave the following output:

java.rmi.RemoteException: This operation requires the Clone-plus plugin be installed on the JIRA server. Remove project and type parameters to use the regular clone operation.
Clone of issue KEY-3 failed.
Remote error: Project 'NEWKEY' created with key NEWKEY.
1 issues failed to be cloned. 0 issues cloned to project NEWKEY.

(The error was that the project was created?!?)

A new project named "Clone" with key "NEWKEY" was indeed created, but it contained no issues, and the configuration from the old project (such as the issue type scheme) was not copied over.  Trying the command again without the --cloneIssues flag gave no error, but the empty project that was created still did not have the old one's configuration.

To top it all off, searching for Cloud plugins with the query "clone project" gives no results.  Is cloning a project in Cloud currently completely impossible?

[Marlene Kegel - codefortynine]

For Jira Cloud we released a marketplace app called Deep Clone for Jira that enables you to clone up to 5000 issues at once.

With our app you can bulk clone issues between projects and issue types without losing attachments, comments and other issue content.

If you have any feedback or feature requests don't hesitate to contact us at support@codefortynine.com.

[Bob Swift]

Let me deal with each point you raise:

1. The native issue clone operation available with JIRA only allows cloning an issue to the same project and only allows changing the summary field.
2. Clone Plus for JIRA provides more extended cloning capabilities.
3. The JIRA CLI uses the native clone operation when cloning an issue only if there are no extended parameters that force the need for Clone Plus for JIRA.
4. cloneProject has options for cloning a number of project attributes including issues with the appropriae use of controling parameters. If the cloneIssues parameters is used, then it attempts to clone issues and must change the project, therefore, it requires Clone Plus for JIRA be installed on the server. Since the add-on is not currently available on Cloud, therefore you cannot clone issues when cloning a project on Cloud. Therefore, you got an error that indicated (in the detail message) that not everything you requested was completed.
5. cloneProject lists various parameters that control what gets copied to the new project. Your action didn't request any of these. 
6. If your need for the cloned project is to create new template projects, then this might be an alternative to cloning issues: How to create projects or sets of issues based on a template