Lyxen
Great Old One
Read the Sage Advice on the topic. It's quite clear that without components, casting is not perceptible and cannot be countered.
I'm well aware of this sage advice, but neither does it say that if a spell has components, then it is perceptible. If nothing is perceptible, then of course, it will not be perceived, but if some things might be perceptible does not mean that they will be by everyone or even anyone.