You can display accordions under any post including custom post dynamically a single accordions or different accordions under different posts,

Display dynamically different accordions under the different posts.

#1. First, you need to set custom meta field  accordions_id under your post.

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#2. Then add the following code to your theme functions.php file or 3rd party PHP code editor plugin.

add_filter('the_content','accordions_after_content_20200520');
function accordions_after_content_20200520($content){
    if(is_singular(array('post'))){ // add your post types here

        $post_id = get_the_id();
        $accordions_id = get_post_meta($post_id,'accordions_id', true); // get accordions id from custom meta field

        if(!empty($accordions_id)){
            $content .= do_shortcode('[accordions id="'.$accordions_id.'"]');
        }
    }

    return $content;
}

#3. Once you have done successfully your accordions will display under post content.

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Display one accordions under all post

Also, you can display one single accordion under all posts in same way. not the value of accordion id 52346 you need to replace by your accordions id.

add_filter('the_content','accordions_after_content_20200520');
function accordions_after_content_20200520($content){
    if(is_singular(array('post'))){ // add your post types here

        $post_id = get_the_id();
        $accordions_id = 52346; // accordions id

        if(!empty($accordions_id)){
            $content .= do_shortcode('[accordions id="'.$accordions_id.'"]');
        }
    }

    return $content;
}