I am trying to use the Google Meet API to join the meeting and capture the audio stream.
I didn't find any API from Google Cloud Console.
As per this Google Community Help Doc,
To enable the Google Meet API and use its features, follow these steps: Access the Google Cloud Console. Create a new project or select an existing one. In the left sidebar, select "APIs and Services" and then "Library". In the search bar, type "Google Meet" and select the Google Meet API. Click the "Enable" button to enable the API in your project. In the left sidebar, select "Credentials" and then "Create Credentials". Select "API Key" and then select "Create". Copy the generated API key and use it in your requests. With the API enabled and the credentials created, you can use the Google Meet API documents to integrate the desired functionality into your application.
In Google Meet there is an option called record, click on the recording button, if it asks permission give the necessary permissions then this will record the audio and screen aswell.
You can also use a screen recording tool or audio recording tool to capture the audio stream, this needs to get a proper consent from Google.
Refer to this Google support doc for tracking attendance, live streaming report.