I’m removing the broken tag.
To begin with, the component was never broken!
There was a misunderstanding about another Discourse theme component that Volanar reported as broken.
I tested the component, which still works on the latest Discourse version.
However, it still requires some updates to modernize it, resolve a deprecation, and fix minor issues so it will work well on the latest Discourse version.
I went ahead and I made a PR (sponsored by @Richard_Millington) 
https://github.com/Ahmedgagan/header-locale-selector/pull/3