MultiplayerService.CreateOrJoinSessionAsync sometimes returns before SceneManager is ready

[afarchy]

Description

I'm hitting an error here that I don't understand in joining a distributed authority session, where after the session joins, the SceneManager is null.

• This doesn't always happen.
• Never seen this in editor, only on device. We're using Meta Quest 2/3.

var options = new SessionOptions()
{
    Name = sessionName,
    MaxPlayers = 64,
}.WithDistributedAuthorityNetwork();

_currentSession = await MultiplayerService.Instance.CreateOrJoinSessionAsync(sessionName, options);

if (NetworkManager.Singleton.SceneManager == null)
{
    Debug.LogError("Why is this happening?");
}

Reproduce Steps

1. See code above

Actual Outcome

NetworkManager.Singleton.SceneManager is null.

Expected Outcome

NetworkManager.Singleton.SceneManager is not null.

Environment

• OS: Meta Quest 2/3 (Android)
• Unity Version: 6000.0.23f1
• Netcode Version: 2.1.1
• Netcode Commit: [e.g. https://github.com/Unity-Technologies/com.unity.netcode.gameobjects/commit/d218b2992ddb98f2eb1a06b9085724ca33352865]