Alternatively, parts of the UK could break off and rejoin the EU (e.g. Scotland). I can't predict whether this will happen or not.
Sinn Fein, the former political wing of the IRA, won elections in North Ireland yesterday:
https://www.reuters.com/world/uk/northern-ireland-poised-wat...
I don't pretend to be an expert on Irish politics. It's unclear to me whether the Republic really even wants North Ireland given its lackluster economy. Maybe it's easier to have London keep sending billions there.
Instructive is https://bbc.co.uk . You can barely find news of this, it is way down the page. Superhero movies, Miami Grand Prix. dating apps, pilota, carbon bicycles etc. take precedence. England doesn't care, other than the loose ends remaining snagged Brexit somewhat.
That Original Sinn Fein splintered into Fianna Fail, Fine Gael, a bunch of random socialist parties, and eventually the workers party which merged with Labour 30+ years ago.
The Sinn Fein that did really well in the NI assembly elections yesterday is Provisional Sinn Fein, which is an outgrowth of the civil rights movement for Catholics that started in the 1960s.
This Sinn Fein was the political wing of the Provisional IRA, an armed group which engaged in violence to bring about a united Ireland.
So, yes they are IRA associated (though the pIRA haven't engaged in political violence since about 1997).