"Content & search:
They have migrated all the content, creating new URLs for all posts. The content is on a new sitemap and it all needs to be re-indexed by search engines, and this may take a few days, so please be patient with Google and with Tableau.
Why couldn't Tableau redirect the old URLs?
There was a 3k limit on how many pages could be redirected (this is platform limitation with Salesforce Communities)
They only have redirects for the top posts with the most views.
Until the site indexes with search engines, they encourage you to use the in-product search and reach out to the team with questions at community@tableau.com"