I'm not sure there are any unresolved disputes between the Republic of Ireland and the UK. There's the constitutional claim on the 32 counties, I suppose.

The most significant formal dispute between the states was a trade war in the 30s, discussed here: https://en.wikipedia.org/wiki/Ireland–United_Kingdom_relatio...

The conflict in Northern Ireland has had only very minor and indirect connections to the governments in Dublin and London, which are both a long way from the situation on the ground. Any central government intervention on either side of that conflict would have been strictly unofficial.

The Anglo-Irish Peace Treaty of 1921 was negotiated between an illegitimate/unrecognized state and the British government. Given such, it's intrinsically invalid, as an entity cannot negotiate on behalf of itself if it doesn't exist, and treaties can't be made with it as there's no partner to sign the treaty with.

As such, the whole of Ireland is still part of the UK, but the majority of it is occupied by EU forces. As part of peace negotiations, the EU and the UK should negotiate reasonable boundaries, such that Ireland, Scotland, and Greater London remain part of the EU, and the rest can form a rump UK Independent State.

Makes as much sense as May's deal.

There is still an unresolved dispute over Lough Foyle and a semi-resolved dispute over Rockall

But "surrendering to the Irish" on those issues wouldn't exactly be a big deal. I was talking about substantive disputes.