Have you ever De-Catholicized Ireland in a Crusader Kings game?

[I spent the winter writing songs about getting better]

Of course. Alas I've never managed to annihilate the Papacy in CK3 yet, is a goal of mine. Although I did manage to actually destroy the Sunni Caliphate in one game, but that was mostly by accident because of how much of an idiot the AI playing the Sunni Caliphate was.

[I spent the winter writing songs about getting better]

BRTD: atheism is cringe.
Also BRTD:

Actually what I did is defeat all the Muslim rulers in Iberia, unify it, invade North Africa and convert some of those Muslim areas, then establish a branch of Christianity like modern day liberal Protestantism for the new empire, win a Crusade the Pope called and then invade Ireland and convert it just as I was eliminating Islam and Catholicism in Iberia and North Africa and converting all of their areas to my new branch. So establishing what's basically Protestantism a few centuries earlier (1285 is over two centuries before the Reformation) and liberal Protestantism even more centuries earlier. I'd assume you would much prefer my new Christianity branch I established with the tenants I chose.

[I spent the winter writing songs about getting better]

Why specifically Ireland? Have you heard of Spain or Poland?

BRTD: atheism is cringe.
Also BRTD:

Actually what I did is defeat all the Muslim rulers in Iberia, unify it, invade North Africa and convert some of those Muslim areas, then establish a branch of Christianity like modern day liberal Protestantism for the new empire, win a Crusade the Pope called and then invade Ireland and convert it just as I was eliminating Islam and Catholicism in Iberia and North Africa and converting all of their areas to my new branch. So establishing what's basically Protestantism a few centuries earlier (1285 is over two centuries before the Reformation) and liberal Protestantism even more centuries earlier. I'd assume you would much prefer my new Christianity branch I established with the tenants I chose.

So yeah I did it in Spain. As for Poland that's not very impressive because it's mostly Slavic pagan at the beginning anyway.