Manual:$wgInterwikiMagic

Details
Treat language links as magic connectors (meta>m:Special:MyLanguage/Help:Interwiki_linking#Interlanguage_link|interlanguage links), not inline links. If   is set to true and   is set to false, interlanguage links (e.g. fr:La Foo) will show up in the sidebar.

An interwiki link is considered a language link if the interwiki prefix matches a MediaWiki stat>Localisation statistics|language code, or if the prefix is present in .

On talk pages, interlanguage links are always parsed as inline links regardless of this setting.