@Sunpriat2 to check I understand correctly:

If an editor adds {{noexternallanglinks}} to any page, the expectation is only Wikidata language links are disabled NOT all language links are disabled?

https://www.mediawiki.org/wiki/Wikibase/Installation/Advanced_configuration#noexternallanglinks

@Jdlrobson For a complete understanding, this was used as a tweak around what the list looks like. For example, there are 317 languages ​​on the main page, if you disable the checkbox "Use a compact language list, with languages relevant to you." in Preferences/Appearance, then these languages ​​will be 6300px in height. When {{noexternallanglinks}} was added, the long list from Wikidata disappeared, but the links left as local interwiki in the wikitext of the page remained and were shown in the sidebar in place of the languages.
It is planned that the languages will be in one button in the header https://www.mediawiki.org/wiki/Reading/Web/Desktop_Improvements/Features/Language_switching , but the main page does not have a header and it is unclear how the button and languages will look on the main page in the future.
Perhaps after the appearance of one button, the setting of disabling the short list will not affect the list in the modern Vector. But the setting will affect monobook and old Vector skins, where some gadgets work with a complete list, for example, moving up certain languages or replacing the names of languages from their writing to names in one local language.
Maybe now all wikis should use noexternallanglinks "as a function, with parameters" if this new change is important or it will work as written "Only the interlanguage links that are present in the wikitext will be used".

It is planned that the languages will be in one button in the header https://www.mediawiki.org/wiki/Reading/Web/Desktop_Improvements/Features/Language_switching , but the main page does not have a header and it is unclear how the button and languages will look on the main page in the future.

You can look at T276140 for some insight into this particular question.

Maybe now all wikis should use noexternallanglinks "as a function, with parameters" if this new change is important or it will work as written "Only the interlanguage links that are present in the wikitext will be used".

As implemented, {{noexternallanglinks}} is disabling all languages on the page. Now I understand this check better, I think the check should be removed completely. When the magic word is used it doesn't mean the page can't have languages it just means to ignore wikidata. That should not be a concern for Vector. It seems every page can have languages except special pages.

In T277517#6943947, @Jdlrobson wrote:

As implemented, {{noexternallanglinks}} is disabling all languages on the page.

Vector V2 is disabling all languages on the page.

Now I understand this check better, I think the check should be removed completely.

To be clear, you mean removing https://gerrit.wikimedia.org/g/mediawiki/skins/Vector/+/ec6bca52eeb763c9bec9da7bd78f2e22300b82d5/includes/SkinVector.php#134, right? If so, then I think that this could be estimated and moved to Ready for Development immediately.

Change 681720 had a related patch set uploaded (by Nray; author: Nray):

[mediawiki/skins/Vector@master] Remove 'noexternallanglinks' check from `canHaveLanguages`

https://gerrit.wikimedia.org/r/681720

Change 681720 merged by jenkins-bot:

[mediawiki/skins/Vector@master] Remove 'noexternallanglinks' check from `canHaveLanguages`

https://gerrit.wikimedia.org/r/681720

Test Result - Beta

Status: ✅ PASS
Environment: beta
OS: macOS Big Sur
Browser: Chrome
Device: MBP
Emulated Device: NA

Test Artifact(s):

QA Steps

Visit https://en.wikipedia.beta.wmflabs.org/wiki/T277517 . This page has the noexternallanglinks in its wikitext, but also includes a local interlanguage link so that languages should still show.
✅ AC1: Ensure that the language button is visible.
✅ AC2: Clicking the language button shows a list containing "Simple English"