Neutrales und skeptisches Gesicht
Even delicate shades of ignorance shouldn't be left unnoticed. It's very important to convey your neutral attitude correctly. Unicode offers a huge variety of emojis for that. Copy them and paste in social media and messengers. Let your interlocutors know how exactly you couldn't care less this time, and what type of «oh whatever» you've chosen today.
Here you can also see a smile with a long nose exposing a liar. A tad of skepticism is the perfect answer you need in this situation.