I have had half a dozen iterations with Amazon, and am still not seeing a clue.
My Kindle collection, including C.J.S. Hayward: The Complete Works, is by physical construction converted from submitted, handcrafted, single-page HTML original documents. This and other works open with front matter, including a table of contents built in HTML, clearly intelligible but without any markup saying "This succession of p.table-of-contents
containing one link each is a table of contents."
Recently I received a Kindle quality notice that my book should have an NCX table of contents. I've repeatedly asked that Amazon either explain how to do that with a plain old HTML original, or withdraw the request. I've repeatedly been pointed to https://kdp.amazon.com/en_US/help/topic/G201605710 and failed completely in my efforts to communicate that the instructions given are ePub-specific and not an option in a single HTML file:
2. Use your TOC as an HTML TOC (recommended)
For customers on older devices, this saves many clicks when they want to jump to a part of your book.
Activate a guide item in the Kindle Go To menu to make a link to the HTML TOC accessible from anywhere in the book. To do this, reference your TOC in the navigation document with a landmarks nav element (sample code below).
In the epub:type attribute, set "landmarks" as the value.
In the epub:type attribute, add a link with "toc" as the value.
Sample code:
<nav epub:type="landmarks">
<ol><li><a epub:type="toc" href="table-of-contents.xhtml">Table of Contents</a></li></ol>
</nav>
What, if any, options are there to make any appropriate changes that are feasible within an HTML source, and/or ask Amazon to stop asking for ePub-specific features on a single non-ePub HTML source?
.mobi
format so it can support their kind of TOC and they can render it unreadable at their whim,, and those with "older devices" can just go hang.