Nick van de Veerdonk

An HTML sitemap is a list of names and links of your pages and posts in the front end of your website. It can be useful for users to get a good overview of the content you’re presenting. For bots it is equally useful since the internal links send them to the farest corners of your website, which could help indexation greatly.
Strictly taken AMP does not need a sitemap (HTML or XML) if the content is marked up correctly: engines know where AMP content is by this piece of code present in your regular pages:
<pre><code><link rel="amphtml" href="https://www.example.com/url/to/amp/document.html">
</code></pre>
That being said there could be several reasons to use an AMP HTML Sitemap:
<ol>
<li>
You want your AMP content to be indexed faster and more regulary. In case you don’t have much traffic, external links or good internal linking structure indexation could take a while. An HTML sitemap will improve your internal links and if you add the URL of the sitemap to your current XML sitemap plugin, search engines will gain information on the AMP content by automatic submission of your XML sitemap. (see ‘Addditonal tips’ under installation tab)
</li>
<li>
You have ‘stand alone’ AMP content. Seen as there are no links pointing to content that is only reachable by AMP (because they miss the link from the regular page and naturally don’t occur in menus) it can take a long time for them to be indexed.
</li>
<li>
You have an HTML sitemap for regular content and simply wish to add your AMP content to it
</li>
</ol>
And in that case, this lightweight plugin is for you.
This plugin will not be supported, I will however try to answer all question in the comment section of the <a href="https://jaaadesign.nl/en/blog/amp-sitemap/" rel="nofollow ugc">plugin website</a> and create a FAQ.
Matt Cutts on HTML and XML sitemaps 
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AMP HTML Sitemap

Only four stars so far, because although the description  says it does posts and pages, I only get posts.

This plugin worked well. After adding the shortcode to my existing sitemap page, there were new links appended with /amp to the AMP posts.  

Great idea for a plugin, and I just now submitted the sitemap page to "Fetch as Google" in the Search Console. I can't yet say if it will speed up Google's  discovery, but I do suspect it will.

***Update*** 
In 24 hours, AMP pages in Google's index went from "none found" for three domains, to well over 50%.  Clearly this plugins does what it's intended to do - helps Google get AMP pages indexed faster.

Worked Perfectly

The links have incorrect endings.
Should be:
site.url/stat-name.html

Actual result:
site.url/stat-name.htmlamp

The links have incorrect endings

Generates a customizable list of your AMP posts, pages and custom post types for SEO/indexing benefits, to be added to the content by shortcode.

wpza

This plugin from WPZA provides your website with a shortcode to display AMP images, rather than using the standard HTML img tags in WordPress.
<h3>Shortcode usage</h3>
To insert the image, you must use the image attribute as such: <code>[amp-img image="https://wpza.net/example-image.jpg"]</code>
To insert the alt text, you must use the alt attribute as such: <code>[amp-img image="https://wpza.net/example-image.jpg" alt="Example image alt text"]</code>

AMP Img Shortcode

We use this on our own website to allow our authors to easily create amp-img shortcodes within their post's content.

We use this

This plugin from WPZA provides your website with a shortcode to display AMP images, rather than using the standard HTML img tags in WordPress.

AMP HTML Sitemap vs AMP Img Shortcode