I was going to (and actually did) delete this post, but after sleeping on it, think it might end up being of some use.
What I was missing, above, is [Template Hierarchy][1]. I was looking at the singular.php
template file, which will only ever be loaded when is_archive()
, is_home()
, etc, aren’t true.
What got me is that the HTML <main>
element exists on both the index.php
and singular.php
documents in this theme.
So I was able to update the child theme’s copy of index.php
:
<main id="site-content" class="flex-container">
With CSS:
.flex-container {
display: flex;
flex-direction: column;
}
/* Responsive layout - make multi-column on larger screens */
@media (min-width: 800px) {
.flex-container {
flex-direction: row;
}
}
Thanks for the solution in the comment, @bosco.
[1]: https://developer.wordpress.org/themes/basics/template-hierarchy/