Magento2 – Fix Missing Headers and Footers on CMS Page

The reason for this behavior is found in the function Mage_Sitemap_Model_Sitemap::generateXml. Here magento loops through the categories, products and cms pages and creates the xml nodes for each item. As you noted in your question the /home entry exists as this is covered by the cms pages.

There are events for manipulating the category and product collections specifically for the sitemap but sadly there are none for the cms pages. I would suggest the following, either:

1. Rewrite Mage_Sitemap_Model_Sitemap and add your own checks/fire a cms event after the collection is loaded,
2. Listen to the collection load after event and check to make sure, the collection is the cms page collection and your request comes from the generation of sitemaps,

With either of these options you should be able to update the value of the url when dealing with the home page to be the website's home url and not the cms page url_key.

After experimenting with the code for a while, I was able to fix the broken theme.

Issue 1

I wrapped all content into the bmg-wrapper container, including before.body.end. Simply removing the following code from the wrapper resolved most of my problems.

<referenceContainer name="before.body.end">
    <block class="Magento\Theme\Block\Html\Footer" name="absolute_footer" template="html/absolute_footer.phtml" />
</referenceContainer>

Issue 2

Out of ignorance that comes with learning Magento 2, I built the foundation of my layout with custom containers, then moved referenceBlock and referenceContainer elements into them. Moving common elements around too much caused my theme to break.

I figured out that I can replace the CSS classes of referenceContainer's with my own, which removed the need to create so many custom containers. I was able to rewrite default.xml using only 4 <move>'s instead of the 17 <move>'s seen in my original code. In addition, the rewritten default.xml file is 40 lines smaller in length.