TYPO3 Core

the correct hreflang-tag-set appears only if there is a setup with multiple fallback languages and existing translation for the first fallback language.

same behavior in the language menu, fallback languages become available.

the crux is, in the language menu i do not want the fallback languages. the language menu should show only real pages. the hfreflang tags may include fallback languages.
therefore it would be nice if the language setup has a config value for hreflang and another for the language menu.
with enabled option set to false, the page is not available in this language at all, so this option is useless.

Will check fallback behaviour. About the wanted difference between the language menu and hreflang: why should the information you give to a search engine (hreflang tags) differ from the information you give to a user?

Ok, I checked this again.

I'm submitting a patch that would include all languages in the hreflang. If you use the language menu processor, you could check for the available parameter on each language to check if you should render the link. Of course, you can also exclude certain languages in the processor configuration.

Patch set 1 for branch 10.4 of project Packages/TYPO3.CMS has been pushed to the review server.
It is available at https://review.typo3.org/c/Packages/TYPO3.CMS/+/67892