This simple OCMOD extension (doesn't modify any system files), allows any Opencart-based E-commerce shop owner to generate a simple Google Reviews feed, base on Google's requirements listed on their documentation page HERE

This is Opencart 2.3.0.2, works seamlessly with any theme, because it doesn't touch and doesn't need to integrate with any theme files, the admin interface integrates in accordance with the basic / default Opencart admin theme.