This message was deleted.

Found the solution. Documentation could be more clear on this topic. But this is the correct code:

Settings = Output.Tuple(hostPool.Name, hostPool.RegistrationInfo).Apply((tuple) =>
                                            {
                                                return new Dictionary<string, object>
                                                {
                                                    { "modulesUrl", "<https://somestorageblob.blob.core.windows.net/galleryartifacts/Configuration_5-5-2021.zip>" },
                                                    { "configurationFunction", "Configuration.ps1\\AddSessionHost" },
                                                    { "properties", new Dictionary<string, object>
                                                        {
                                                            { "hostPoolName", tuple.Item1 },
                                                            { "registrationInfoToken", tuple.Item2.Token },
                                                            { "aadJoin", false },
                                                        }
                                                    }
                                                };
                                            }
                                        )
            });