How to customise the default language sitemap url in a multilanguage Hugo website

Question

I have a multilanguage website in Hugo and right now the sitemap generated automatically is the following:

<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <sitemap>
   <loc>https://domain/en/sitemap.xml</loc>
   <lastmod>2022-04-20T08:34:57+02:00</lastmod>
  </sitemap>
  <sitemap>
   <loc>https://domain/it/sitemap.xml</loc>
   <lastmod>2022-04-20T08:34:57+02:00</lastmod>
  </sitemap>
</sitemapindex>

The issue is that all the content in English, which is the default language, does not contain /en in the url but simply the slug itself, such as /products /blog. The italian content contains the language indication in the url instead, such as /it/prodotti, /it/blog.

Sitemap-wise, it doesn't seem to be advisable to have the english sitemap in /en/sitemap. It should be in /domain/sitemap_en.xml instead.

Any clue on how to customise the localised url of the sitemap?

Thank you.