How to export all messages in a Google Group?

I'm attempting to download a copy of all messages from a Google Group. I am an owner of the group.

According to https://support.google.com/accounts/answer/3024190#zippy=%2Cim-a-member-of-a-google-group-how-can-i-download-messages-and-membership-info-from-the-group owners should be able to download such a copy, but I cannot see anything to do so in the Groups UI.

I also attempted to use Google Takeout for this purpose, but the archive contains only the memberlist. That list has un-redacted email addresses, so it does recognise that I am a group owner - but no messages are included in the archive. According to https://support.google.com/groups/answer/9975859?hl=en#zippy=%2Cinformation-about-groups-you-own I believe it should contain it, but the memberlist is all I get.

What is the correct path for a group owner to get a copy of the group's messages?