Multihost site on Netlify

I have a multi-host multilanguage Hugo setup (I got the setup here).

Now I’m deploying my project to Netlify. All domains are connected, and the language switcher redirects to the proper URL, but the content remains in english. Like if I created a site, and connected 3 domains, i.e. language conf in hugo.toml absolutely ignored

At the same time, the local run creates 3 web servers (for the moment I have 3 languages), the languages switcher works, redirects to the proper URL, and content is translated)

I would start here:
https://answers.netlify.com/t/hosting-two-sites-at-one-url-status-codes-monorepo/802/4