If liqueur means sweet, I never drink them nowadays but sometimes we use them in cooking. Nothing is better for rounding off a meal and for removing an excessively lingering sweet taste from the dessert than a dry spirit such as Cognac, Armagnac, Calvados, malt Whisky, grappa (or marc de Bourgogne, etc.) and dry fruit brandies like Framboise, Poire, Prune Sauvage, etc.
I have been living in Normandy for nearly 10 years and the trou normand is a thing of the past when Normans sat down to multi course meals with dishes cooked with lashings of butter, cream and cheese. As the name suggests, it was intended to make room for the next rich course and I don't think it was ever proposed as an apéritif. I can't recall ever having been offered a Calvados in this guise even in the many decades of visiting Normandy before I settled here.