I received mine today. In the package is an HTML page that lets you see your Miiverse posts page as the original Miiverse interface. If you don't see it, check other folders such as promotions (that's where mine was), spam, bin, etc. If you still don't see it, fear not, it seems everyone didn't get them at once.
A few directories of interest:
Handwritten posts: assets/user/img/pa
Your mii expressions: assets/user/img/mii
You have until December 31st 2017 to download the package.
We had a good session promoting MV Haven on Miiverse in its final hour with no administrative repercussions and that has evidently raised enough awareness for the community numbers to have doubled recently. Thanks to all those who got involved, and welcome to those who answered the call! This seems to have been further enhanced by a couple of other channels suffering downtime. The Miiverse Memories section has been updated with a user's farewell video and my own capturing of its final moments.
The music section has been changed to YouTube playlist format because I was previously using the same service as for my art section which only allows 5 audio and it rendered me unable to add more art. I actually think it's better this way as the thumbnails were designed for YouTube anyway so those now appear correctly.