Language handling with RewriteRules only

language-handling.conf

RewriteEngine on

# Language detection (Fallback is en)
RewriteCond %{HTTP:Accept-Language} ^de [NC]
RewriteCond %{ENV:lang} ^$
RewriteRule ^ - [E=lang:de]

RewriteCond %{HTTP:Accept-Language} ^fr [NC]
RewriteCond %{ENV:lang} ^$
RewriteRule ^ - [E=lang:fr]

RewriteCond %{HTTP:Accept-Language} ^it [NC]
RewriteCond %{ENV:lang} ^$
RewriteRule ^ - [E=lang:it]

RewriteCond %{HTTP:Accept-Language} ^en [NC,OR]
RewriteCond %{ENV:lang} ^$
RewriteRule ^ - [E=lang:en]

# now the example with a rewriterule
RewriteRule ^/?$ https://%{HTTP_HOST}/index.html#lang=%{ENV:lang} [L,R=301,NE]