Sunrise.php for WordPress multisite nested subdirectories. Credits: https://medium.com/@heyjones/how-to-get-wordpress-multisite-to-allow-nested-paths-on-bedrock-c3bca0f69c3a

sunrise.php

<?php
if( defined( 'DOMAIN_CURRENT_SITE' ) && defined( 'PATH_CURRENT_SITE' ) ){
 $current_site = new stdClass;
 $current_site->id = defined( 'SITE_ID_CURRENT_SITE' ) ? constant( 'SITE_ID_CURRENT_SITE' ) : 1;
 $current_site->domain = $domain = DOMAIN_CURRENT_SITE;
 $current_site->path  = $path = PATH_CURRENT_SITE;
 if( defined( 'BLOGID_CURRENT_SITE' ) ){
  $current_site->blog_id = BLOGID_CURRENT_SITE;
 }
 $url = parse_url( $_SERVER['REQUEST_URI'], PHP_URL_PATH );
 $patharray = (array) explode( '/', trim( $url, '/' ) );
 $pathsearch = '';
 $blogsearch = '';
 if( count( $patharray ) ){
  foreach( $patharray as $pathpart ){
   $pathsearch .= '/' . $pathpart;
   $blogsearch .= $wpdb->prepare(" OR (domain = %s AND path = %s) ", $domain, $pathsearch . '/' );
  }
 }
 $current_blog = $wpdb->get_row( $wpdb->prepare( "SELECT *, LENGTH( path ) as pathlen FROM $wpdb->blogs WHERE domain = %s AND path = '/'", $domain, $path ) . $blogsearch . 'ORDER BY pathlen DESC LIMIT 1' );
 $blog_id = $current_blog->blog_id;
 $public = $current_blog->public;
 $site_id = $current_blog->site_id;
 $current_site = pu_get_current_site_name( $current_site );
}
function pu_get_current_site_name( $current_site ){
 global $wpdb;
 $current_site->site_name = wp_cache_get( $current_site->id . ':current_site_name', "site-options" );
 if( !$current_site->site_name ){
  $current_site->site_name = $wpdb->get_var( $wpdb->prepare( "SELECT meta_value FROM $wpdb->sitemeta WHERE site_id = %d AND meta_key = 'site_name'", $current_site->id ) );
  if( $current_site->site_name == null ){
   $current_site->site_name = ucfirst( $current_site->domain );
  }
  wp_cache_set( $current_site->id . ':current_site_name', $current_site->site_name, 'site-options' );
 }
 return $current_site;
}