@freatt please try adding the read:jira-user to list of scopes in your manifest - it should unblock the endpoint for you. From the message it sounds like you have the read:user:jira declared in manifest but not the read:jira-user (those are technically two totally different scopes).
To clarify what the error message means:
- expected scopes for this endpoint are
[read:user:jira, read:application-role:jira, read:avatar:jira, read:group:jira](app needs all of them) - it is also possible to access the endpoint with just
read:jira-user
Jira APIs are already ahead with rollout of new scopes so it’s a bit futuristic state - due to situation explained in Deprecated Scope Warning. Because of that Jira already suggests that read:jira-user is deprecated (which technically is not yet true as the deprecation did not started yet).