Sitemap feed multilanguage

Hello everyone. I recently added a second language (Greek) in my oc and I'm trying to include it in my sitemap, I use different SEO_URL for each language. The extension that I use is the default one and it generates an xml based on the current language each time, at least that's what I understand.
I red that it's not a good idea to add two separate xml sitemaps in google, it hurts seo and thinks they are two different things. Is there another extension that can do this in a single xml with hreflang ?

Version 3.0.3.8
default theme
PHP: 7.3.13

The default sitemap extension doesn't support this functionality out of the box. You'll need to review the code in:

catalog/controller/extension/feed/google_sitemap.php

To achieve the desired output, you must modify the code accordingly. This includes adapting it to cover all relevant parts of your site, such as products, categories, manufacturers, and information pages, so they respond correctly for each language.