NOTE: This suggestion is for JIRA Cloud. Using JIRA Server? See the corresponding suggestion.

Oauth 2 is already available for Jira Core and Jira Service Desk REST API endpoints:

• https://developer.atlassian.com/cloud/jira/platform/oauth-2-authorization-code-grants-3lo-for-apps/
• https://developer.atlassian.com/cloud/jira/service-desk/oauth-2-authorization-code-grants-3lo-for-apps/

And for a subset of the endpoints available for Jira Software Cloud:

• https://developer.atlassian.com/cloud/jira/software/integrate-jsw-cloud-with-onpremises-tools/

The feature request to have also the other endpoints supported is: JSWCLOUD-18874

You can see whether Oauth2 is supported or not for an endpoint by checking if the documentation is mentioning:

OAuth scopes required: XXXXX