Chat plugin works out of the box after activating it. The plugin checks current language ( ChatPlugin::get_current_language() ) on init and returns instantly if language is English. Please note that language check is based on Polylang's function pll_current_language(). So if your site is not using that plugin, make sure the language check works.
Chat.js is based heavily on the code provided by IBM.
In case of modifying needed:
composer installnpm ci && npm run watch