Question Part of the code below cannot be type-converted by the method of reading the next scene asynchronous

I am using Pun2.
I am writing a program that asynchronously transitions scenes (rooms).
at the moment, so far

Code (CSharp):

1. privateAsyncOperation_async;
2. _async = SceneManager.LoadSceneAsync(SceneName);
3. _async.allowSceneActivation = false;
4. ・
5. ・
6. ・
7. ・
8. _async.allowSceneActivation = true;

I was able to do it with the above process,
With asynchronous loading when connecting to PhotonNetWork,
_async = PhotonNetwork.LoadLevel(scene name);
When I change it as above, I get the below error

error CS0029 cannot implicitly convert type 'void' to 'UnityEngine.AsyncOperation'

The question is, in addition to how to resolve the above error (type conversion),
Can PhotonNetWork load next scene asynchronously before scene transition?[/code]