Stephen AfamO

This plugin allows you to use any HTML or PHP file as the template for any page or post.
Simply upload the file and select it. 
You can upload custom js and css files into the media library and link to them from the HTML file.
Options:
<ul>
<li>Overwrite All: You overwrite the entire theme and use your custom file</li>
<li>Overwrite Content: Keeps the header, footer, sidebar, e.t.c. Simply overwrites the body of the page or post</li>
<li>Above Content: Your custom content is simply added to the top of the page content</li>
<li>Below Content: You custom content is placed just beneath the page content.</li>
</ul>
<h4>Adding support for custom post types</h4>
By default the pulugin works with pages and posts, however, go to the settings to enable it on any other registered post type.
use the <code>hppp_post_types</code> filter to add more post types.
Like this:
<pre><code> public function post_type_modify ($post_types) {
 $post_types[] = 'custom_post_type';
 return $post_types;
 }

 add_filter( 'hppp_post_types', 'post_type_modify' );
</code></pre>

Custom HTML/PHP Post Templates

I use this on a couple sites I own and it works wonderfully.
I hope you can find it useful. 

Works like a charm

Use your HTML or PHP files for any page or post.

vegacorp

Jose Vega

Green Jay Media

<ul>
<li>
Easily convert posts into landing pages
</li>
<li>
Hide headers on single posts pages
</li>
<li>
Remove the logo, menu, and the entire page header when viewing posts
</li>
<li>
No code required. You just enable the option when creating posts and done. 
It works with all WordPress themes.
</li>
</ul>
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/spyrpgd-oyA?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>
<h3>How it works</h3>
Using a creative way we’re able to find the header on posts and hide it.
It works with all WordPress themes.
It’s great for creating landing pages out of your WordPress posts.
<h3>Go Premium</h3>
The free version lets you hide headers on single posts only.
<a href="https://wppagetemplates.com/try-hide-headers-wporg" rel="nofollow ugc">Try Pro Plugin for Free for 7 Days</a>
The premium version lets you hide headers and sidebars on ALL POST TYPES.
<ul>
<li>
Hide headers on pages / Convert pages into landing pages
</li>
<li>
Hide headers on product pages / Convert products into landing pages
</li>
<li>
Hide headers on the WooCommerce cart page and increase conversions
</li>
<li>
Hide headers on the WooCommerce checkout page and increase sales
</li>
<li>
Hide headers on event pages / Convert events into landing pages
</li>
<li>
Hide headers on any post type / Convert any post type into landing pages
</li>
<li>
Hide sidebars on pages / Make any page full width
</li>
<li>
Hide sidebars on event pages / Make events full width
</li>
<li>
Hide footer on posts, pages, products, events
</li>
<li>
Make the WooCommerce cart page full width
</li>
<li>
Make the WooCommerce checkout page full width
</li>
<li>
And more.
</li>
</ul>
<a href="https://wppagetemplates.com/try-hide-headers-wporg" rel="nofollow ugc">Try Pro Plugin for Free for 7 Days</a>
<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/c2KBLNvQWzA?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>

Custom HTML/PHP Post Templates vs Hide Header on Posts for Landing Pages