Page Structure Tutorial: Change guidance to suggest that main should only contain main content
Looking at the code snippet on https://www.w3.org/WAI/tutorials/page-structure/example/
It shows the main starting with an article, and the first thing in the article is a TOC.
At least for screen reader and keyboard users, the best use of main is to draw the user right into the main content in the same way that good visual design brings gaze to the most important content. There is nothing worse, as a screen reader user, then having to skip past a bunch of links at the start of main, especially if the main content is an article. And, there is nothing better than a site that uses main well.
Ideally, the first thing in main is a heading immediately followed by content. If there is stuff between the heading and the main content, then a good work around is to put the heading outside of main and have it label main. Then, when you jump to main you get the benefit of hearing that main is what you expect and then you dive right into the meat ... 0 wasted time.
An article TOC, if part of the design, can be in a nav outside of main. However, TOCs for the main content of the current page are a rare entities because they only provide value on extremely long pages, which aren't all that common ... except on w3.org, of course.
Similarly, it is also best if breadcrumb nav regions are outside of main.
Thanks for the input @mcking65. We will certainly consider this for the next revision of the tutorial.