Lake Geneva is the English name commonly used to refer to Lac Léman. I suspect you know that, but I don't follow why you object to that name.
This is very common. The name used by the locals is called endonym and the one used by foreigners is the exonym.
For example Zhōnghuá is the endonym vs China the exonym. Or Magyarország vs Hungary. Or Deutschland vs Germany. Or so I not just list English exonyms Lake Balaton vs Plattensee.