i18n locales shows 404

[fast spoke]

I just started a new nextjs project with i18n config, but if I try to access the localized page, it shows 404 error.
next.config.js

  i18n: {
    defaultLocale: "en",
    locales: ["en", "ko"],
  },

I have not added any other code and just visited the homepage
localhost:3000/ - shows the correct page
localhost:3000/ko - shows an error

added info:
I'm using the app/ folder here. Does i18n work on app/ or just on pages/ ?

am I missing something here?

[verbal quiver]

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