Some airports will carry your duty-free after gate check like in the US, but some won't and just give it to you right at purchase
However, there are some articles that are quite sizable due to how they're packed (like a cardboard box around the item), with no chance of being packed into existing luggage or even the possibility that the existing cabin luggage is full.
What are the airlines stance on duty-free purchases contributing to cabin luggage allowance when not able to pack such purchases in existing luggage?