According to Get Google Group emails with Gmail API (and threads far in the past), there wasn't any main method to support querying conversations directly for Google Groups within a domain after listing existing Google Groups (https://developers.google.com/admin-sdk/directory/reference/rest/v1/groups/list). Has this changed, or is the recommended method still to:
- List the existing groups via the Directory API above
- Query emails for messages with filter "to:<google_group>"
To my knowledge, this also doesn't cover a variety of edge cases, such as Google Group Conversations that may have been deleted from inboxes, tracking emails sent to the Google Group that might have failed the send (from message not being approved or sender not having permissions), etc.