How to set default template for custom post type from a plugin.

1. Create the Custom Template File:

First, create a template file that you want to use as the default template for your custom post type. For example, create a file called single-work.php (assuming your custom post type is work).

You can store this file within your plugin’s directory, for example: /my-plugin/templates/single-work.php.

2. Use the template_include Filter to Override the Template:

In your plugin, use the template_include filter to specify the custom template for your custom post type.

function my_plugin_custom_post_type_template( $template ) {
    if ( is_singular( 'work' ) ) {
        // Define the path to the template file inside your plugin
        $plugin_template = plugin_dir_path( __FILE__ ) . 'templates/single-work.php';
        
        // Check if the template file exists
        if ( file_exists( $plugin_template ) ) {
            return $plugin_template;
        }
    }
    return $template;
}
add_filter( 'template_include', 'my_plugin_custom_post_type_template' );

Example structure of single-work.php:
Make sure that your custom template file (single-work.php) follows WordPress’ template structure, including get_header(), get_footer(), etc

<?php get_header(); ?>

<div id="primary" class="content-area">
    <main id="main" class="site-main">
        <?php
        while ( have_posts() ) :
            the_post();
            // Custom template content for 'work' post type
            the_title( '<h1>', '</h1>' );
            the_content();
        endwhile;
        ?>
    </main>
</div>

<?php get_footer(); ?>

Thanks @mayuripatel!

I was searching for a way to do this for block themes, not classic themes. This should also be reflected on the backend as well.

Thank you anyway!