Alias / to /lang_code I got a multilanguage configuration with language detection based on URL(/en /fr). Drupal behavior redirects everything to so it would have those two prefixes or, if setup, it will ignore the prefix for a language while keeping for the other.

In my situation I need to keep the prefix for both language except for root page.

Ex:


example.com/en -> will load english homepage
example.com/fr -> will load french homepage
example.com/ -> has to load english homepage but without redirect to /en


So, how can this be achieved?
Drupal core doesn't redirect everything. Do you have the Redirect module installed? Then disable the route normalizer in the module settings, which is by default enabled:
/admin/config/search/redirect/settings

GLOBAL REDIRECTS
[x] Enforce clean and canonical URLs

If you want to keep the global redirect try this module specifically for the language prefix Disable Route Normalizer.