AppFlowy

AppFlowy is the most powerful open-source alternative to Notion, boasting 72k stars. It features a local-first architecture that stores data locally, giving users complete control over their privacy. The app supports various views such as documents, databases, Kanban boards, and calendars. It includes built-in AI capabilities for assisting with writing and content generation. Available as a cross-platform desktop application (Windows/Mac/Linux) as well as a mobile version, it offers a plugin system for custom extensions. It’s ideal for individuals and teams who need Notion’s functionality but prioritize data privacy and open-source principles.