Hi there,
Welcome to the Auth0 Community!
After looking into this, it appears that we currently do not have any official documentation or guideline for integrating Auth0 for Tanstack, besides this following Dev to Dev discussion where a link to Tanstack’s website was provided by my colleague, which is likely the same one that you were following.
I can advise that you submit a Feature Request on this, which other users can vote on. Our Product team has visibility over the Feedback page and enough engagement can help the development of the idea.
While you can find information on other online sources, please approach any unofficial documentation with a great deal of care to stay secure and always run tests in a secure, non-production environment.
Hope this helped!
Gerald