Ryan Johansson's father has confirmed that Ryan had not an irish passport when he first played international competitive football for Luxembourg
Johannson’s father clarified the specific details of these paperwork issues in an interview of his own, in which he stated that at the time Johansson had first played for Luxembourg at Under-21 level, he did not have an Irish passport, whereas he did already hold both a Luxembourg passport and a Swedish passport.
As nationality and citizenship are synonomous terms you can take it that Ryan is not entitled to declare for Ireland,
It's possible that Ryan's foreign birth was registered but I'd say that's a longshot.