Exclude folder – htaccess

Hi!

I need to exclude 1 folder (and all subfolders and files inside) in the root, say “folder” so it works without WP.
I have subdirectories based Network with standard .htaccess:

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]

What’s missing here? Because subfolders are still shown by WP…

RewriteEngine On
RewriteBase /
RewriteRule ^/folder($|/) - [L] 
RewriteRule ^index\.php$ - [L]