Looking for a Roblox-style Game Source Code / Ready-Made Engine Template (Full-Stack & Multiplayer Ready)

Hello everyone,

I am currently looking for a complete, ready-to-use game source code or architecture template similar to Roblox—or a modular sandbox MMO framework—that covers both the client and server sides.

Instead of building a voxel/user-generated content platform completely from scratch, I want to find a robust baseline project that already has the core infrastructure set up.

Here are the specific requirements I am looking for:

Architecture & Codebase: Clean, scalable architecture (MVC or component-based) with well-organized code.

Frontend / UI/UX: Responsive user interface, menu systems, inventory layout, and HUD elements already implemented.

Backend & Server Integration: Fully integrated server-client networking, player authentication, matchmaking or room management, and database connection.

Tech Stack: Open to modern stacks (e.g., Node.js/TypeScript backend with Three.js/Babylon.js/Unity/Godot on the frontend, or custom C++/.NET architectures).

If you know of any open-source projects, GitHub repositories, commercial boilerplates, or game templates that fit this description, please share them below. Any recommendations or advice on where to find production-ready sandbox frameworks would be greatly appreciated!

Thanks in advance!