It is a Ryanair contract not with the broker. I was informed by Ryanair that according to Portuguese regulation you have to pay local tax on domestic sectors and it applies to all items of your salary. That is why I find it quite confusing. The biggest issue here is you expecting a certain take home pay and when you get your pay slip surprise it wasn´t even close.
In another exercise if you make lots of domestic flights/working days you achieve a scenario where you pay the lowest tax in Ireland and in Portugal, although at the end of the year you can find yourself paying a huge bill to the tax man.