Using $seed on a custom post type for randomly displayed posts

This is untested, but I think it should work. Add the filter in pre_get_posts if it’s your post type archive, otherwise remove it for any queries that follow the post type archive main query.

function wpd_add_posts_orderby( $query ){
    if( $query->is_post_type_archive('your-cpt') ){
        add_filter('posts_orderby', 'edit_posts_orderby');
    } else {
        remove_filter('posts_orderby', 'edit_posts_orderby');
    }
}
add_action( 'pre_get_posts', 'wpd_add_posts_orderby' );