I'll iterate one last time, I will not put extra effort in to support private servers, if someone wants to figure out what they've done, which is, again, likely a new encryption key or a new encryption, then feel free to figure it out yourself.
A few people asked how to find the encryption and/or the key, without knowing what that entails, it means reverse engineering either the game binary or the game during runtime, or both.
Alternatively you could ask their devs to share what they've done to make this a lot less complex, but they're unlikely to do so.