Recommended directory structure for multilingual websites

Is the recommended directory structure for multilingual websites

  1. non-translated slugs

/en/about/_index.md
/fr/about/_index.md

or

  1. translated slugs
/en/about/_index.md
/fr/a-propos/_index.md

?

I read that 2. is the best in terms of SEO, telling users exactly what the page is about and also achieving better CTR. On the other hand, I also read that 1. is Hugo team’s recommended approach as it simplifies the language switcher logic while hreflang, which seems to be more important for SEO than slugs, is still generated accordingly.

I would highly recommend that you normalise the path element of the content to one language (e.g. English). Note that this path does not need to be the end path, you can e.g. set up the permalinks config to use e.g. the slug value for the final URL.