My understanding is that Bank of Ireland UK PLC, Ulster Bank, and Danske Bank still have sterling notes in circulation and legal. First Trust Bank did not issue polymer notes so their paper notes ceased to be legal currency last year.
It is certainly confusing that the official currency of Ireland is the euro, but Bank of Ireland does not issue euro notes but issues Sterling notes.
Now if we want to discuss Irish, English and Scottish Groats.......🤣🤣