How to implement multilingual sitemaps when not all pages have translations

[Telsenome]

We are trying to implement sitemaps for a site that has localized content for a few countries. We’ve concluded that we should utilize sitemapindex and then create one sitemap per country. Now to the problems we’re facing.

Not all urls on the site have translations, how should these urls be presented in the sitemap? Should they be stated simply like so?

<url><loc>https://example.com/sdfsdf</loc></url>

So urls with the hreflang attribute and without are mixed in the same sitemap, or is that a problem? (I have added empty rows to make it easier to read)

<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" <br="">xmlns:xhtml="http://www.w3.org/1999/xhtml"></urlset>

<url><loc>http://www.example.com/english/page.html</loc>
<xhtml:link rel="alternate"  hreflang="de"  href="http://www.example.com/deutsch/page.html"><xhtml:link rel="alternate" hreflang="de-ch" href="http://www.example.com/schweiz-deutsch/page.html"><xhtml:link rel="alternate" hreflang="en" href="http: www.example.com="" english="" page.html"=""></xhtml:link rel="alternate" hreflang="en" href="http:></xhtml:link></xhtml:link></url>

<url><loc>http://www.example.com/page-with-no-translations</loc></url>

<url><loc>http://www.example.com/page-with-no-translations2</loc></url>

<url><loc>http://www.example.com/page-with-no-translations3</loc></url>

<url><loc>http://www.example.com/deutsch/page.html</loc>
<xhtml:link rel="alternate"  hreflang="de"  href="http://www.example.com/deutsch/page.html"><xhtml:link rel="alternate"  hreflang="de-ch"  href="http://www.example.com/schweiz-deutsch/page.html"><xhtml:link rel="alternate" hreflang="en" href="http://www.example.com/english/page.html"></xhtml:link rel="alternate"></xhtml:link></xhtml:link></url>

[Telsenome]

Additional question about which parts should go into which sitemap. The url https://example.com/us/driver-guides/railroad-crossings has 3 "translations". Where should all these <url>elements go? We've used a Google sheet provided by Ahrefs to create these. </url>

This one is for us so it should be put in the us sitemap? (sorry about the code block being single line, I don't understand why they're not multi line)

<loc>https://example.com/us/driver-guides/railroad-crossings</loc>

This one is for uk so it should be put in the uk sitemap?

<loc>https://example.com/uk/car/level-crossings</loc>

This one is for se so it should be put in the se sitemap?

<loc>https://example.com/se/bil/jarnvagskorsningar</loc>

This one is the same as the first one. I assume it's for the "x-default" attribute. Where should it be put?

<loc>https://example.com/us/driver-guides/railroad-crossings</loc>

[Telsenome]

I continued to think about the matter and thought of this approach for adding the pages with no localization to the multilingual sitemap (just putting it here):

<url><loc>https://example.com/page-with-no-localization</loc></url>

Or is it better to put a simple link to the page in the sitemap?

<url><loc>https://example.com/page-with-no-localization</loc></url>