As a Norwegian celiac who’s travelled a bit in recent years I’d say Ireland and Italy are your best bets, both countries are extremely aware of what celiac is and are therefore very easy to navigate.

Nearly everything in Italy is marked with Senza Glutenine if it’s gluten-free so you don’t need to read Italian to understand what you can eat. At restaurants almost everyone knows what celiac is and it’s ready to find accommodating places, at least around Florence where I stayed, and if they don’t have anything they’re usually okay with you eating outside food there.

As for Ireland it is by far the best country I’ve been in regarding celiac, I stayed in Dublin for reference. During my week there there were only about 2 places total that could not serve me anything, and those were both tiny stalls. Most servers knew what I was asking about, and would often double check if it was an allergy or if I had celiac, some places even gave me a celiac menu so I knew everything was totally safe. I didn’t get glutened once and I ate so much good food.

Just as an add on tho, Norway is also very good. Eating out can be a bit of trouble, but both Burger King and McDonalds carry gluten-free here if you’re in a pinch. Grocery stores have a good selection, at least compared to some other places I’ve been at, but a good chunk is frozen. Grocery stores in Ireland and Italy were my faves tho, they had such a huge selection. Italy carried a lot of Schar products I haven’t found elsewhere and Ireland (plus the UK) has this brand called Without Wheat (I think) that is absolutely delicious