Ironically this seems like a perfect use for AI from the maintaner side. "Find low-effort/AI-like PR's without associated issues from new contributors. Discuss with the contributors in the PR about how contributions should be made, then reject their PR's. If any bad behavior is detected in this interaction, block the accounts for 24 hours and add them to a list of accounts to review for permanent banning from the project".
Automated PR's can have automated responses. You make a human effort, you get a human response.
Automated PR's can have automated responses. You make a human effort, you get a human response.