Is it possible to force the site to make the default language Russian (HTTP_ACCEPT_LANGUAGE)?

Question

Browsers

Hello, help me.
Site on Wordpress + Woocommerce (in CMS settings - Russian).
Plugin WC Fields Factory (additional fields for admin and order). The plugin has multilingual support, it concerns the translation of labels for fields, placeholders, etc. The plugin looks at HTTP_ACCEPT_LANGUAGE and outputs everything in one language or another.
Problem: on the same computer, in Chrome and Firefox browsers - everything is in English, in Safari in Russian (as it should be). It does not depend on authorization by the user. All browsers with a Russian version, in the console of each, the priority language, if checked through navigator.language - Russian (RU).

Answer 1

Manually set $_SERVER["HTTP_ACCEPT_LANGUAGE"] = "..." in index.php or anywhere before the plugin.