$ wp site option get subdomain_install
1

$ wp site option get illegal_names
array (
      0 => 'www',
      1 => 'web',
      2 => 'root',
      3 => 'admin',
      4 => 'main',
      5 => 'invite',
      6 => 'administrator',
      7 => 'files',
      8 => 'blog',
)

RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*.php)$ $2 [L]
RewriteRule . index.php [L]

RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*.php)$ $1 [L]
RewriteRule . index.php [L]

// patch-forbidden-slugs.php
<?php
$illegalNames = get_metadata( 'site', SITE_ID_CURRENT_SITE, 'illegal_names', true );
$blogSlug = 'blog';
if ( in_array( $blogSlug, $illegalNames ) ) {
    exit( 'Noting to do' . PHP_EOL );
}
$illegalNames[] = $blogSlug;
update_metadata( 'site', SITE_ID_CURRENT_SITE, 'illegal_names', $illegalNames );
exit( 'Done' . PHP_EOL );