I personally have a French boon. account. It doesn't really matter either way as the limits with basic (also in Ireland) are far too low anyway. Also there articles indicating you HAVE to download the boon. app from the countries App Store you want later in boon. But that's simply not true. I installed mine via my UK Apple ID and set it up with the region set to France but language left on English (UK). So as long as you have access to an Apple ID in a country that has the boon app, install it from there and choose your region before setting up your account. Also: Terminals are usually in German, sometimes I have messages in English and my monthly statement is also in English, despite using boon. France.
Several people are reporting blocked Apple IDs (check Apfel.cash) when setting up a foreign account. I can't check if this is true or not. Also the question is how long Apple will permit users setting up foreign boon. accounts. Legally it isn't really problem as you can - as a European citizen - open an account in any EU country you want. Boon. gets around this by offering you a French / Irish / whatever MasterCard. But look at what happened to bunq...