Generate an offline minecraft UUID v3 based on the case sensitive player name, based on https://gist.github.com/games647/2b6a00a8fc21fd3b88375f03c9e2e603

Offlinenametouuid.cs

private string GetOfflinePlayerUUID(string username)
{
    //new GameProfile(UUID.nameUUIDFromBytes(("OfflinePlayer:" + name).getBytes(Charsets.UTF_8)), name));
    byte[] rawresult = System.Security.Cryptography.MD5.Create().ComputeHash(Encoding.UTF8.GetBytes($"OfflinePlayer:{username}"));
    //set the version to 3 -> Name based md5 hash
    rawresult[6] = (byte)(rawresult[6] & 0x0f | 0x30);
    //IETF variant
    rawresult[8] = (byte)(rawresult[8] & 0x3f | 0x80);
    //convert to string and remove any - if any
    string finalresult = BitConverter.ToString(rawresult).Replace("-", "");
    //formatting
    finalresult = finalresult.Insert(8, "-").Insert(13, "-").Insert(18, "-").Insert(23, "-");
    return finalresult;
}