Adding in Vivox package. There is now a basic voice channel while in a lobby, but not yet volume controls or other Vivox features. (There are some TODOs of details to follow up on as well.)

Assets/Scripts/Game/GameManager.cs

         private LobbyContentHeartbeat m_lobbyContentHeartbeat = new LobbyContentHeartbeat();
         private RelayUtpSetup m_relaySetup;
         private RelayUtpClient m_relayClient;
+        private vivox.VivoxSetup m_vivoxSetup = new vivox.VivoxSetup();
 
         /// <summary>Rather than a setter, this is usable in-editor. It won't accept an enum, however.</summary>
         public void SetLobbyColorFilter(int color)
             m_localUser.ID = Locator.Get.Identity.GetSubIdentity(Auth.IIdentityType.Auth).GetContent("id");
             m_localUser.DisplayName = NameGenerator.GetName(m_localUser.ID);
             m_localLobby.AddPlayer(m_localUser); // The local LobbyUser object will be hooked into UI before the LocalLobby is populated during lobby join, so the LocalLobby must know about it already when that happens.
+            m_vivoxSetup.Initialize(null);
         }
 
         private void BeginObservers()
             m_lobbyContentHeartbeat.BeginTracking(m_localLobby, m_localUser);
             SetUserLobbyState();
             StartRelayConnection();
+            m_vivoxSetup.JoinLobbyChannel(m_localLobby.LobbyID);
         }
 
         private void OnLeftLobby()
             m_lobbyContentHeartbeat.EndTracking();
             LobbyAsyncRequests.Instance.EndTracking();
+            m_vivoxSetup.LeaveLobbyChannel();
-            {
-                Component.Destroy(m_relaySetup);
+            {   Component.Destroy(m_relaySetup);
-
-            {
-                Component.Destroy(m_relayClient);
+            {   Component.Destroy(m_relayClient);
                 m_relayClient = null;
             }
         }

Assets/Scripts/LobbyRelaySample.asmdef

         "GUID:5540e30183c82e84b954c033c388e06c",
         "GUID:fe25561d224ed4743af4c60938a59d0b",
         "GUID:4c3f49d89436d478ea78315c03159dcc",
-        "GUID:f2d49d9fa7e7eb3418e39723a7d3b92f"
+        "GUID:f2d49d9fa7e7eb3418e39723a7d3b92f",
+        "GUID:060a730ab4d4804498f4a3146ed6f776",
+        "GUID:6087a74f6015aae4daed9a2577a7596c"
     ],
     "includePlatforms": [],
     "excludePlatforms": [],

Packages/manifest.json

     "com.unity.services.core": "1.0.0",
     "com.unity.services.lobby": "1.0.0-pre.4",
     "com.unity.services.relay": "1.0.1-pre.1",
+    "com.unity.services.vivox": "15.1.150000-pre.6",
     "com.unity.sysroot.linux-x86_64": "0.1.15-preview",
     "com.unity.test-framework": "1.1.27",
     "com.unity.textmeshpro": "3.0.6",

Packages/packages-lock.json

       },
       "url": "https://packages.unity.com"
     },
+    "com.unity.services.vivox": {
+      "version": "15.1.150000-pre.6",
+      "depth": 0,
+      "source": "registry",
+      "dependencies": {
+        "com.unity.settings-manager": "1.0.3",
+        "com.unity.services.core": "1.1.0-pre.8",
+        "com.unity.nuget.newtonsoft-json": "2.0.0"
+      },
+      "url": "https://packages.unity.com"
+    },
+    "com.unity.settings-manager": {
+      "version": "1.0.3",
+      "depth": 1,
+      "source": "registry",
+      "dependencies": {},
+      "url": "https://packages.unity.com"
+    },
     "com.unity.sysroot": {
       "version": "0.1.19-preview",
       "depth": 1,

Assets/Scripts/Vivox.meta

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+folderAsset: yes
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Assets/Scripts/Vivox/VivoxSetup.cs

+using System;
+using Unity.Services.Vivox;
+using VivoxUnity;
+
+namespace LobbyRelaySample.vivox
+{
+    /// <summary>
+    /// Handles setting up a voice channel once inside a lobby.
+    /// </summary>
+    public class VivoxSetup
+    {
+        private bool m_hasInitialized = false;
+        private bool m_isMidInitialize = false;
+        private ILoginSession m_loginSession = null;
+        private IChannelSession m_channelSession = null;
+
+        /// <summary>
+        /// Initialize the Vivox service, before actually joining any audio channels.
+        /// </summary>
+        /// <param name="onComplete">Called on complete, whether successful or not. Not called if already in the middle of a previous Initialize call.</param>
+        public void Initialize(Action onComplete)
+        {
+            if (m_isMidInitialize)
+                return;
+            m_isMidInitialize = true;
+
+            VivoxService.Instance.Initialize();
+            Account account = new Account(Locator.Get.Identity.GetSubIdentity(Auth.IIdentityType.Auth).GetContent("id"));
+            m_loginSession = VivoxService.Instance.Client.GetLoginSession(account);
+
+            m_loginSession.BeginLogin(m_loginSession.GetLoginToken(), SubscriptionMode.Accept, null, null, null, result =>
+            {
+                try
+                {
+                    m_loginSession.EndLogin(result);
+                    m_hasInitialized = true;
+                }
+                catch
+                {
+                    throw;
+                }
+                finally
+                {
+                    m_isMidInitialize = false;
+                    onComplete?.Invoke(); // TODO: Is BeginLogin guaranteed to call this callback?
+                }
+            });
+        }
+
+        /// <summary>
+        /// Once in a lobby, start joining a voice channel for that lobby. Be sure to complete Initialize first.
+        /// </summary>
+        public void JoinLobbyChannel(string lobbyId)
+        {
+            if (!m_hasInitialized || m_loginSession.State != LoginState.LoggedIn)
+            {
+                UnityEngine.Debug.LogWarning("Can't join a Vivox audio channel, as Vivox login hasn't completed yet.");
+                return;
+            }
+
+            ChannelType channelType = ChannelType.NonPositional;
+            Channel channel = new Channel(lobbyId + "_voice", channelType, null);
+            m_channelSession = m_loginSession.GetChannelSession(channel);
+
+            m_channelSession.BeginConnect(true, false, true, m_channelSession.GetConnectToken(), result =>
+            {
+                m_channelSession.EndConnect(result); // TODO: Error handling?
+            });
+        }
+
+        /// <summary>
+        /// To be called when leaving a lobby.
+        /// </summary>
+        public void LeaveLobbyChannel()
+        {
+            ChannelId id = m_channelSession.Channel;
+            m_channelSession?.Disconnect(
+                (result) => { m_loginSession.DeleteChannelSession(id); }); // TODO: What about if this is called while also trying to connect?
+        }
+
+        /// <summary>
+        /// To be called on quit, this will disconnect the player from Vivox entirely instead of just leaving any open lobby channels.
+        /// </summary>
+        public void Uninitialize()
+        {
+            if (!m_hasInitialized)
+                return;
+            m_loginSession.Logout();
+        }
+    }
+}

Assets/Scripts/Vivox/VivoxSetup.cs.meta

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