RewriteEngine on
# Remove www from URL
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
# Redirect HTTP to HTTPS
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]
# Some old URLs start with "en", just drop it
RewriteRule ^en/(.*)$ /$1 [R=301,L]
# Make .html optional
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ $1.html [L]