Ready to next stage button
You can mark the issues with the "ready to next stage" label. After you move the issue, the ready label will be removed automatically.
You can configure column for auto-closing issues.
You can find option in settings to allow read-only access to private board. It's works for private and public GitHub repositories.
Issues due dates
Board Markdown Export
Can try at our board https://agileseason.com/boards/agileseason/agileseason