As of writing, "a default lobby name will be chosen instead" means that the lobby will be named after your Steam persona name.
    [SourceLocation("Systems\\Networking\\Transports\\SteamLobby\\SteamLobbySocket.cs", 76)]
    private void LoadConfig(LobbyConfig config) // SteamLobbySocket.LoadConfig
    {
        if (!string.IsNullOrEmpty(config.Name))
        {
            Networking.UpdateServerName(config.Name);
            SteamLobby.SetData("name", config.Name);
        }
        else
        {
            Networking.UpdateServerName(Sandbox.Utility.Steam.PersonaName ?? "");
            SteamLobby.SetData("auto_name", "1");
            SteamLobby.SetData("name", Sandbox.Utility.Steam.PersonaName ?? "");
        }
    }
(Irrelevant code has been omitted)