NocoBase

NocoBase is an open-source, self-hosted, low-code/no-code development platform that aligns well with the concept of Retool. It emphasizes extensibility through a plugin-based architecture and allows users to build internal tools and business systems. It explicitly mentions features like API & Database Integrations, a visual UI builder, code customization through plugins, access control and security features (SSO, RBAC, audit logs), flexible deployment options (self-hosted, Docker), debugging and monitoring tools, version control integration (Git), and workflow automation. While it doesn't explicitly state 'drag-and-drop UI builder' in those exact words, it describes a visual composition of interfaces with 'What you see is what you get' and 'Pages serve as a canvas where various blocks and actions are placed to compose suitable interfaces', which strongly implies a drag-and-drop functionality. The platform also supports AI/LLM integration as a commercial plugin, further aligning with the broader concept.