Firstly, you can't use an OAuth 2.0 request path with a clientID in Forge apps. You must only use a request path with the URI structure that is valid for Forge apps, as stated in the Authentication and authorization section of Jira's REST API documentation.

Secondly, no Forge app can "fetch Jira data across multiple installed orgs" because that is breach of the basic security principles of Forge apps and all the Atlassian apps... Tenant Isolation!. You could have found the answer to that Frequently Asked Question with a Google search of "With an Atlassian Forge app, can I fetch Jira data across multiple installed orgs?"