Isn't this literally because there's no translations for sma and smj in Babel?

So there's no way for MW to give them in those translations, as they don't exist

https://translatewiki.net/wiki/MediaWiki:Babel-1/sma etc

https://translatewiki.net/wiki/Special:Translate?group=ext-babel&language=sma&filter=&action=translate
https://translatewiki.net/wiki/Special:Translate?group=ext-babel&language=smg&filter=&action=translate

In T255515#6226589, @Reedy wrote:

Isn't this literally because there's no translations for sma and smj in Babel?

So there's no way for MW to give them in those translations, as they don't exist

https://translatewiki.net/wiki/MediaWiki:Babel-1/sma etc

Well, the messages in Translatewiki don't actually contain the language name, it is replaced with a placeholder $3. In Translatewiki itself, the messages – even if untranslated – don't show "English", but rather the autonym or the English name. See e.g. https://translatewiki.net/wiki/Portal:Smj and https://translatewiki.net/wiki/Portal:Sma . So the question becomes: Why do the language names – show up correctly on Translatewiki and not on Meta?

When I first saw this bug I assumed it was because smj is not in Names.php, but sma is in Names.php, so it's weird that that one also shows "English". Then I thought maybe it was related to the CLDR extension, but TWN and Wikimedia wikis both run the same version of that extension, so that can't (or shouldn't) be it.

Adding @Nikerabbit who probably knows why this is (or knows how to figure it out…). And to be clear, this affects almost all language codes that don't have Wikimedia wikis, not just smj and sma.

It seems to be that it's falling back to https://meta.wikimedia.org/wiki/MediaWiki:Babel-0-n isntead of https://meta.wikimedia.org/wiki/MediaWiki:Babel-0. I think that if these messages are removed locally, fallback order may be restored.

Well, yes, because the autonym is not in CLDR nor Names.php. The fact that it's not in CLDR is an upstream issue, while the fact that it's not in Names.php (yet) is because the language hasn't reached the translation threshold to be added there.

Neither of these things have anything to do with MediaWiki-extensions-Babel. The original bug you reported, the language names being shown as "English" (and only on Meta & global user pages from Meta, as it turns out), has been solved.

The other issue would be resolved by T190129: Consolidate language metadata into a 'language-data' library and use in MediaWiki

This issue is left half-done, but who cares.

You can also add names to LocalNamesSmj.php in the cldr extension, but I have not verified if it gets loaded.