Use a custom sitemap template for multilingual site

I have been using the following custom sitemap template for my site.

<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  {{ range .Data.Pages }}
  <url>
    <loc>{{ .Permalink }}</loc>
  </url>
  {{ end }}
</urlset>

Basically the only thing I want in my sitemap is the <loc> node.
I started translating my site content to English and since I added a new language, Hugo creates the following sitemap files

/sitemap.xml
/fa/sitemap.xml
/en/sitemap.xml

/sitemap.xml points to the other two files that list the pages for each language. But this /sitemap.xml adds a <lastmod> node which I do not want and I don’t seem to find a way to provide a custom template for this. Here is the content for /sitemap.xml:

<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
	
	<sitemap>
	   	<loc>https://www.mysite.com/fa/sitemap.xml</loc>
		
	   	<lastmod>2016-08-29T00:00:00+00:00</lastmod>
		
	</sitemap>
	
	<sitemap>
	   	<loc>https://www.mysite.com/en/sitemap.xml</loc>
		
	   	<lastmod>2017-03-14T00:00:00+00:00</lastmod>
		
	</sitemap>
	
</sitemapindex>

Is this at all possible?
Hugo v0.18.1

A post was split to a new topic: Excluding taxonomies from sitemaps in multilingual sites