Dublin is a gluten free paradise! You can get gluten-free food on almost every street corner. In addition, you regularly see that the restaurant is 'celiac friendly' and they therefore also take cross-contamination into account.
3 restaurants where I've had a great experience:
Number 1 is without a doubt Beshoff Bros, delicious fish and chips from a separate fryer!
For a delicious pizza (and more) in a cozy atmosphere, go to the Gotham Café. The staff are very well informed and they call themselves 'celiac friendly'.
You can enjoy an extensive dinner or lunch at Millstone Restaurant with a separate menu for celiacs.
In addition, there are plenty of restaurants with good gluten-free options in Dublin. Before you go, download the FindMeGlutenFree app and read reviews from other gluten-free travelers. You can also read lots of reviews on Tripadvisor.
Enjoy the cozy city and the delicious gluten-free food!