Problem with Virtualmin, Letsencrypt and redirect to https in the .htaccess file

Virtualmin
2

Try with this:
RewriteEngine On
RewriteCond %{HTTPS} off [OR]
RewriteCond %{HTTP_HOST} !^www. [NC]
RewriteCond %{HTTP_HOST} ^(?:www.)?(.+)$ [NC]
RewriteRule ^ https://www.%1%{REQUEST_URI} [L,NE,R=301]

Just copy/paste, it will work with any domain.