Hi,
In context, enabling language tags from Multilingual Plugin 🌐 - plugin - Discourse Meta is part of the multilingual experiments for two weeks; See Notes from #MetaBrainz Meeting 2023-11-27
The plugin uses Discourse’s mapping of locale codes en to “English (US)” (which should normally be “English”) and en_GB to “English (GB)”. I agree that the regional variant doesn’t make sense here since most users are from other countries anyway, but I didn’t find how to remove it so far.