The actual sitemap tool don't allow us to add some additional information to each<loc>entry to output a Multilingual sitemap. As specified from Google tells to add an<xhtml:link>child entry for every different language variation of each piece of content (including the original language). So if our content is available in English (default) and French, we should have two<xhtml:link>child entries for each<loc>entry.
This is definitely necessary - especially as HubSpot focuses on securing more "upmarket" customers that tend to have larger, multi-language sites - particularly as the sitemap is used for onsite search.
Another push. Multilanguage Siteweb with only generic sitemap, it's crazy. SEO google need a generic sitemap, a table of content of the single language sitemaps. For example: www.mywebsite.com/sitemap.xml must contains: