Sylvain Chiron, 17/04/19 00:33:
I’d say it would be cool however if changing the language at the top would also try to go to localized version of the current page.
That's already the case in MediaWiki.org because $wgTranslatePageTranslationULS is true. https://www.mediawiki.org/wiki/Help:Extension:Translate/Configuration#Configuration_variables
The problem is that [[Main page]] is not a translatable page, [[Template:Main page]] is. The easy solution is to move the template and avoid transclusion.
Federico