Start with the provided link to browse a sample collection that is an example of Webrecorder's capabilities to collect a public Yahoo Group, which is on the open web and available without needing to log in to a Yahoo account.
A 'representative sample' of Yahoo Groups content can be obtained for public groups using a customized autopilot behavior in Webrecorder. This collection contains materials going back to some point in 2018 but this collection is not a full copy of the contents of the Yahoo Group (which has been active since 2012).