I came across this upon install too, I use Advanced Custom Fields and it too has a native ‘Duplicate’ action. I was able to exclude the Post Duplicator buttons/link by doing the following.
function excludeDuplicatorAction($actions, $post){
$postType = get_post_type();
if(in_array($postType , array('acf-field-group'))):
if(isset($actions['duplicate_post'])):
unset($actions['duplicate_post']);
endif;
endif;
return $actions;
}
add_filter( 'post_row_actions', 'excludeDuplicatorAction', 11, 2 );
add_filter( 'page_row_actions', 'excludeDuplicatorAction', 11, 2 );
add_action('pre_get_posts' , function(){
global $post;
$postType = get_post_type($post);
if(in_array($postType , array('acf-field-group'))):
remove_action('post_submitbox_misc_actions' , 'mtphr_post_duplicator_submitbox');
endif;
},10);