With a POD of 1919 how can you get an Ireland that is divided by the River Bann? Bonus points for West Belfast being included as a West Berlin-style enclave.
The problem with discrimination in Northern Ireland is twofold and I think both factors would still have told against Catholics: 1) Michael Collins intelligence war involved a brilliantly successful co-option of Nationalist moles in the RIC, Civil and Prison Services. Stormont thereafter were unwilling to allow Catholics into key posts in the RUC or Civil Service and very reluctant to allow them into those bodies at all; 2) Masonry played a key role in Stormont politics and administration and top political and administrative jobs tended to be delivered to 33K Masons. Now Masonry does not ban Catholics per se, the problem is other - the Roman Catholic Church bans its communicants from becoming Masons. So I fear some discrimination is inescapable even if less severe than OTL.Discrimination could possibly be somewhat less of an issue. As the Unionist majority becomes more secure, the less need for overt discrimination.
@ShortsBelfast
Defections of border councils if two home rule delivered two parliaments. Seems harder to stop a contiguous council moving from one semi- autonomous region of the UK to another.
You wouldn't get a Communist arriving in power in twentieth century Ireland North or South. Land ownership was widely dispersed, most businesses were small and religious observance very high in the early to mid C20th and fairly high in the mid to late C20thIreland has a Castro-type figure who’s less successful and turns the eastern portion red? Then you have a partitioned Ireland AND the possibility of Soviet nukes in Britain’s backyard.