I’ve also been to Dublin and Madrid. The Dublin frum community is incredibly tiny — at most a dozen shomer Shabat families — but incredibly friendly. There is a kosher-friendly guest house a short walk from the synagogue and the bus system goes everywhere. Dublin even has a small Jewish museum. (And yes, everything coming out of the Guiness brewery is kosher.) No kosher restaurants but there was a kosher caterer who operated out of the synagogue kitchen who will send food anywhere on the island. It is an English speaking country with an Ashkenazic English speaking Jewish community — the synagogue used Artscroll siddurim. Ireland has basically no history of anti-Semitism; there is one Jewish school that gets government funding. No eruv.
Madrid has a somewhat larger community but they were mostly away on holiday while I was there, so I really can’t say much except that the synagogue (Sefardic) is VERY hard to find. There was a nice small Best Western hotel just a few blocks away, and there were two kosher restaurants, both Moroccan cuisine. No eruv there, either.
Enjoy!