I have seen a similar question somewhere here, but I can’t find it and I don’t think it included a suitable solution.

Let’s consider a scenario where we work with the following languages and domains

cs-CZ, en-GB, en-US, de-DE, fr-FR, it-IT

www.example.cz 
www.example.com 
www.example.fr 
www.example.it

For whatever reason en-GB, en-US, and de-DE need to share one domain, which is www.example.com

We want to show news in each and every language on the following URLs

www.example.cz/novinky 
www.example.com/news
www.example.com/en-us/news 
www.example.com/de-de/aktualiten
www.example.fr/nouvelles 
www.example.it/notizia

It would be easy if there was a domain for every language, or all languages were hosted on a single domain, or all domains started with www.domain.xx/xx-xx/news

I could put in my router.ex

Enum.each ["/:locale", ""], fn locale ->
    scope locale, PlutoWeb do
      pipe_through [:browser, :ensure_redirect]

      get "/", PageController, :index
    end
  end

but then how will I know whether :locale is an actual language or just news?

If I go with www.domain.xx/xx-xx/news for every language, the issue is that URLs will be ugly for websites, where there will just be one language.