We are trying to give customers access to our Knowledge Base created in confluence through our Service Project by following the instructions on the following link:
https://support.atlassian.com/jira-service-management-cloud/docs/manage-knowledge-base-permissions-from-your-service-project/
We adjust the access from Confluence side to the following:

And this is how the linked space appears when looking at it from the JIRA Service Management Side:

(I do suspect that this 'Who can view' limitation is the issue as it seems to refer to a different User Type than the one described below).
Our Customers have Access as 'Service Desk Customers' in the relevant Service Project and access through the front-end Portal like this:

Our expectation is that they could search within the linked Knowledge Base when creating a Request from the Portal.
What can we do to grant our customers access to search our linked Knowledge Base from the JIRA Service Management Portal without giving the whole world access to the knowledge base or having to make them all Users either of Confluence or JIRA.