How to access data as a servicedesk customer in a 3rd party app


we do have a JSM which is used by different endusers. The idea is to display accessible ticket details in a different system.
As basic auth is deprecated I tried to use oauth2.
When I login with an agent then I can get some details back. When I login with a servicedesk user I do not receive information back.
I found the ticket [JSDCLOUD-4065] Enable OAuth for JIRA Service Desk customers - Create and track feature requests for Atlassian products. but not sure if this exactly covers my case.

Can you please let me know if my approach is possible at all and what would be the correct way to access the data?