Problems with hreflang

We're having trouble setting the hreflang. The following is currently displayed for our website.
Example French start page:








Our SEO agency says the correct hreflang must be:







Google Reference:
https://developers.google.com/search/docs/advanced/crawling/localized-versions?hl=en "For each variation of the page, include a set of elements in the element, one link for each page variant including itself. The set of links is identical for every version of the page."

=> The "including itself" is missing and our "set of links" is not identical on every page.
Can this be adjusted somewhere?

Hello Lefteris, thanks for your reply.
We had the "Add x-default Meta Tag" option enabled from the start.
Nothing changes there. The agency says you need 2 lines for the default language in the hreflang:


and


Whether I enable the option or not, the default language only has one line of code
Did you look at the reference from google?

Regards

Hello, thank you. We put the code in the index.php file of the child theme. Unfortunately we don't see any changes. Is the index.php correct?

Hi, There seems to be indeed a problem in Joomla Core. The hreflang seems really buggy. A user from the community wrote a plugin for it: https://github.com/TheWhykiki/seolanghref?fbclid=IwAR1uOHo800VzdlxGTeJQg3BWZ_LLtXAIQ5OWnOAvZmWMYnEqN5Or9qUl2HI