If you are a developer interested in packet analysis or C# reverse engineering, the projects on GitHub offer a challenging and educational sandbox. But for players? Your time is better spent playing the official game, waiting for a deep sale, or revisiting Diablo 2 Resurrected (which has a fully functional plug-in emulator in "D2R Offline").
If you compile the most advanced public emulator today, here is what you will find: diablo 4 server emulator work