Show Widgets Only on Certain Page Types

// Choices for the "Show on" setting added to every classic widget.
$wpide_widget_contexts = array(
    ''            => 'All pages',
    'front'       => 'Homepage only',
    'not_front'   => 'Everywhere except the homepage',
    'singular'    => 'Single posts and pages',
    'posts'       => 'Single blog posts only',
    'lists'       => 'Blog, archive and search pages',
    'not_lists'   => 'Everywhere except blog, archive and search pages',
);

add_action( 'in_widget_form', function ( $widget, $return, $instance ) use ( $wpide_widget_contexts ) {
    $value = isset( $instance['wpide_show_on'] ) ? $instance['wpide_show_on'] : '';
    $id    = $widget->get_field_id( 'wpide_show_on' );

    echo '<p><label for="' . esc_attr( $id ) . '">Show on:</label> <select class="widefat" id="' . esc_attr( $id ) . '" name="' . esc_attr( $widget->get_field_name( 'wpide_show_on' ) ) . '">';

    foreach ( $wpide_widget_contexts as $key => $label ) {
        echo '<option value="' . esc_attr( $key ) . '"' . selected( $value, $key, false ) . '>' . esc_html( $label ) . '</option>';
    }

    echo '</select></p>';
}, 10, 3 );

add_filter( 'widget_update_callback', function ( $instance, $new_instance ) use ( $wpide_widget_contexts ) {
    $value = isset( $new_instance['wpide_show_on'] ) ? sanitize_key( $new_instance['wpide_show_on'] ) : '';

    $instance['wpide_show_on'] = isset( $wpide_widget_contexts[ $value ] ) ? $value : '';

    return $instance;
}, 10, 2 );

add_filter( 'widget_display_callback', function ( $instance ) {
    if ( ! is_array( $instance ) || empty( $instance['wpide_show_on'] ) || is_admin() ) {
        return $instance;
    }

    $is_list = is_home() || is_archive() || is_search();

    switch ( $instance['wpide_show_on'] ) {
        case 'front':
            $show = is_front_page();
            break;
        case 'not_front':
            $show = ! is_front_page();
            break;
        case 'singular':
            $show = is_singular();
            break;
        case 'posts':
            $show = is_singular( 'post' );
            break;
        case 'lists':
            $show = $is_list;
            break;
        case 'not_lists':
            $show = ! $is_list;
            break;
        default:
            $show = true;
    }

    return $show ? $instance : false;
} );