I am not gluten intolerant, but rather the sorts of foods that I must avoid for two overlapping reasons, in veg, are coincidentally (AFAIK) very high in lectin concentration, and gluten is a lectin.
So there can be multiple reasons why someone might need to avoid such foods, and whilst I personally could eat oats from time to time and by exception, the diet that I need to aim for on the Camino is based on steak and eggs.
Beer is OK, though I don't know if the fact that the brewing process eliminates virtually all the lectins, including the vast majority of the gluten, is relevant - - because at the same time there are some lectin-rich veg that seem to do me little harm even when eaten raw.
It's complex stuff, as it would seem that a majority of autoimmune conditions are uncatalogued, which can lead some non-coeliacs to adopt similar dietary strategies in a sledgehammer approach. In some extreme cases, that can lead people to avoid ALL veg always, and require them to use vitamins and other supplements to compensate, though in my case that's some occasional veg, plus some daily vitamin K because I have to avoid greens especially. Quite rarely I need some greens regardless, even though eating them leads to 24 hours increased inflammation and pain.
As to the topic though, once you have understood that the Spanish are generally happy to provide substitutes in composed dishes, including in daily menus (couple of weeks ago in Frómista I got a scrambled eggs and mushrooms starter instead of the seafood one I couldn't eat), you can usually get by, though I do recognise that it's a bit easier for me from not being a coeliac as such, because I can "cheat" occasionally. And sometimes even need to.