it is not too hard to find vegan alternatives in ireland. the biggest shops carry everything you need and even the smaller shops in small villages carry the basics. bigger shops like: tesco, dunnes, supervalue have whole shelves dedicated to healthy and/ or alternative foods and products.
the main shop I relay on is tesco. they have their own home brand called “free from” and also carry a lot of other brands that are vegan. just be careful, not everything from the free from range is actually vegan, but most of the time they are well labelled.
the great thing in tesco is that they have several sections where you can find vegan options. one for example is called free from, the other is whole foods and you are able to find vegan options in the freezer section as well.
shops like lidl and aldi are fantastic for your everyday basics like oats, milk alternatives, rice, etc. I also keep an eye on their fresh fruit and veg section. both shops tend to rotate their special offers on them every week and you can end up buying peaches, tomatoes potatoes, etc for like 49c!
if you are looking for something a bit fancier or more specialised you are better off to check one of the many health food shops. they usually sell nutritional yeast, tofu and other interesting things. they are great for chocolates and ice creams as well.
one thing I never really look out for is things you can but on bread or crackers. like I am happy out just eating whole foods and spreading avocado or hummus on my food. I can give no good suggestions about where to go for any good vegan bread spreads, since I don’t eat them, but I do believe that you can find some in a good health food shop, if you really want some. if not your best option is probably to pack some before you get here.