If your goal is to test upcoming features rather than hosting a private server, Pearl Abyss provides an official Global Lab Client for players with a character level 56 or higher.

A MySQL or MariaDB instance to host the game's world and user data.

One of the most well-known open-source projects. You can often find the source code on platforms like RaGEZONE . These projects typically require you to build the server files using software like Visual Studio (e.g., VS 2012 or 2015).

Because these files are hosted on third-party sites, always scan downloads for malware.