Schlussmitlustig
The German Translation for Revel's End is "Schlussmitlustig". I found it looking through German review videos of Keys of the Golden Vault, it can be see on top of the map here.
The name is a portmanteau of the phrase "Schluss mit lustig!" which translatedtranslates to "The Party is over!" or literally "It's the end of (being) funny!". In that regard it is a far more humorous name, than the gloomy "Revel's End", so one might have to adjust their game's tone a bit, if they plan to use the translated name.
This means the untranslated version on D&D Beyond is actually a mistake, as the name is in fact translated inside the book. Perhaps it was released before the book was fully translated?