Userdoc supports native integration with Jira (using a Jira API key), and actually supports multiple Jira integrations, meaning you can sync your User stories across multiple platforms.
A Userdoc account, and an existing project you wish to integrate with Jira.
A Jira Cloud account, with an existing project you wish to integrate with (Note: Userdoc only supports integration with cloud-hosted Jira, not with Jira Server)
Inside project settings in Userdoc, click Story Integration, then click on the Connect a Jira Cloud Project button
Once this information has been entered, click Next Step