The "raw data" for the reports is just "the issues the report looks at", so if you run a search for the issues it is reporting on (often as simple as "project = XYZ" and updated > -30d"), then you'll be able to use the download option on the tools to get a spreadsheet-friendly dump of the raw data.
The data used for the different reports is different, and so some may be accessible by JQL and others not so much...
The example report you noted, the "Cumulative Flow Diagram" (JIRA's version), uses issue change history, and that is not all accessible by JQL query.
Please see this other community post for ideas how to do this: JIRA add-ons for Excel or Google Sheets, the REST API, log extraction via webhook, or marketplace add-ons for purchase.
Hey there Cloud Community members! We’re excited to give you the first glimpse of the new home for business teams on Jira — Jira Work Management. Jira Work Management is the next generation of Ji...
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