Question: Is there a free and open-source CMS that offers advanced access control, versioning, and localization features for managing complex content structures?

If you're looking for a free and open-source CMS with advanced access control, versioning, and localization support for managing complex content structures, Payload could be a good choice. It's an open-source, headless CMS written in TypeScript and React that's designed to help developers, marketers and product owners work together. Payload includes AI-powered content generation, visual editing, more than 20 field types, access control and strong localization support. It also supports versioning and draft previewing, making it a good choice for agencies and developers who want a flexible and extensible foundation.

Another good option is Sanity, which offers a Composable Content Cloud for creating and managing continuous digital experiences. It comes with an extensible editing environment, real-time collaboration and built-in AI Assist for content help. Sanity supports localization for unified messaging and integrates with tools like Shopify and Mux. It offers APIs for querying content with GROQ and can be used for everything from e-commerce and marketing sites, so it's a good choice for complex content management.

For a low-code option, NocodeCMS is also worth a look. This free, open-source CMS fills a gap between collaboration and control over Webflow CMS data, with an Airtable-like interface for unlimited editors. It supports AI-generated content, 35+ field types, and image/file storage in Firebase. NocodeCMS goes beyond Webflow CMS limits by offering better collaboration and data management abilities, so it's a good option for teams that need a flexible and affordable option.

Last, Contentful is a digital experience platform that makes it easier to create and deliver content to any channel. It offers a composable content platform, intelligent automation and flexible design. Contentful is geared for large-scale enterprises and integrates with more than 100 apps. It offers a free plan and is used by companies like Kraft Heinz and Vodafone, so it's a powerful option for managing complex, multichannel content structures.