Latest Posts From the Main Site on Any Subsite

if ( ! is_multisite() ) {
    return;
}

add_shortcode( 'wpide_main_site_posts', function ( $atts ) {
    $atts = shortcode_atts( array( 'number' => 5, 'category' => '' ), $atts, 'wpide_main_site_posts' );
    $key  = 'wpide_main_posts_' . md5( absint( $atts['number'] ) . '|' . sanitize_title( $atts['category'] ) ) . '_' . (int) get_site_option( 'wpide_main_posts_ver', 1 );
    $html = get_site_transient( $key );

    if ( false === $html ) {
        switch_to_blog( get_main_site_id() );

        $posts = get_posts( array(
            'numberposts'      => min( 20, max( 1, absint( $atts['number'] ) ) ),
            'category_name'    => sanitize_title( $atts['category'] ),
            'no_found_rows'    => true,
            'suppress_filters' => false,
        ) );

        $html = '';
        if ( $posts ) {
            $html = '<ul class="wpide-main-site-posts">';
            foreach ( $posts as $post ) {
                $html .= sprintf(
                    '<li><a href="%1$s">%2$s</a> <time datetime="%3$s">%4$s</time></li>',
                    esc_url( get_permalink( $post ) ),
                    esc_html( get_the_title( $post ) ),
                    esc_attr( get_the_date( 'c', $post ) ),
                    esc_html( get_the_date( '', $post ) )
                );
            }
            $html .= '</ul>';
        }

        restore_current_blog();
        set_site_transient( $key, $html, 15 * MINUTE_IN_SECONDS );
    }

    return $html;
} );

add_action( 'transition_post_status', function ( $new, $old, $post ) {
    if ( is_main_site() && 'post' === $post->post_type && ( 'publish' === $new || 'publish' === $old ) ) {
        update_site_option( 'wpide_main_posts_ver', (int) get_site_option( 'wpide_main_posts_ver', 1 ) + 1 );
    }
}, 10, 3 );