I don't think that Donnarumma can cause any harm to Inter attackers by preventing them from scoring. Inter has more of classic attackers than Arsenal and Inter uses counter attack to net the post. I don't see how Donnarumma presence will scare Martinez and the rest from finding the back of the net. Don't forget that Sommers is also a good goalkeeper to stop PSG from scoring just like he did to Barcelona.
Inter Milan's defense this season has been extraordinary and there is no doubt because it has been shown repeatedly by Inter Milan in big matches this season. So PSG must really be aware of this if they want to beat Inter Milan because I actually prefer PSG to win the Champions League this season so that the team can at least have one Champions League trophy that they have not won so far. But Inter Milan are also very hungry for the trophy so Inter Milan will also do everything they can to win in the final match this season.