Integrating Jira Service Desk with Confluence should allow you to link between Cloud sites with different domains

Problem Definition

Jira Service Desk Cloud will allow you to link with a Confluence space in order to serve customers with a knowledgebase. Currently though this feature requires that both Service Desk and Confluence applications exist in the same Cloud site (with the same Cloud domain name: example.atlassian.net for instance). The documentation in Link a Confluence space to your service desk confirms this.
Right now, it's not possible to link a JSD on example.atlassian.net with a Confluence space found on sample.atlassian.net , even if you have an application link created there, and have permissions to do so.

Suggested Solution

It would be helpful if this integration could be implemented with two different Cloud sites, or one Cloud site and one Server site.

Why this is important

Easier integrations for users spread across different platforms

Workaround

Currently this feature is only available to Cloud sites where Confluence and JSD are on the same site