Tyler Tork

This lightweight plugin hides all featured images on pages and posts when they are viewed in their own tab. The posts are not modified — they still have a featured image if you selected one. The plugin only disables the theme’s ability to access the image when rendering the page. If your theme displays featured images in search results, Posts page, category lists, and so on, it still can do that. Social media platforms and search engines that look for an image to accompany the excerpt, can also still find the featured image URL in the post metadata.
There are no settings; the plugin just does the one thing.
The change applies to existing posts as well as anything you create after activation. You would need to edit any old posts that are adversely affected by this change (if you want the featured image to display, you would have to insert it into the content). If you have a lot of old content, you might want to use a different plugin such as <a href="https://wordpress.org/plugins/conditionally-display-featured-image-on-singular-pages/" rel="ugc">Conditionally display featured image on singular pages and posts</a>, which by default only affects new posts.
TECHNICAL NOTE
Themes that find the featured image by looking up data in the database directly as opposed to calling <code>get_the_post_thumbnail()</code> or <code>wp_get_attachment_image()</code>, may still emit HTML for the featured image despite this plugin. As a second line of defense, the plugin loads a stylesheet that tries to hide the image if it is present in the HTML. This also might fail if the theme has used unusual entities and class names. Custom CSS rules should always be possible as a fallback (in which case you don’t need this plugin).
This plugin also (not on purpose) blocks the featured image from appearing in the content where you’ve inserted a “Post featured image” block. I’m looking into whether it might be possible to detect the difference between a request for the featured image for default display versus a deliberate insertion later. In the meantime, as a workaround, don’t use the “Post featured image” block, but instead insert an “Image” block and re-select the image from your media library (I prefer that anyway since it gives more control over size, alt text, etc).
If you find a theme this doesn’t work with, please let me know.
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Hide featured image on all single page/post

This lightweight plugin hides all featured images on pages and posts when they are viewed in their own tab. The posts are not modified -- they still h …

Lucy Tomas

Very simple plugin that will search for all the first images of your published posts, pages or custom post types and set them as the featured image.
<ul>
<li>You can choose the post type you want to run the plugin on.</li>
<li>Option to overwrite the already selected futured images.</li>
<li>Option to select From / To date.</li>
</ul>

Set All First Images As Featured

still works

It simply didn't recognize any images in any of the posts, and so didn't work. :(

Didn't see the images in the posts

IT works on 5.0.3

Sets the first image of your posts, pages or custom post types as the featured image.

Hide featured image on all single page/post vs Set All First Images As Featured