Ukraine is a war zone now. NI has been at peace in practice since 1998. Both places have been invaded by an aggressive neighbor, rebelled, made peace, etc for hundreds of years.
Your comfort with the current NI situation doesn’t prevent historical comparison.
Yes, Ukraine is a warzone. That war is almost universally condemned.
Northern Ireland is at peace. Its constitutional position within the a United Kingdom is recognises by the Irish government, the British government and all of the other states of the world. This position was agreed through a referendum held for the people of the island almost 30 years ago.
Historical comparison doesn't come into it. The point your were raising was that there was a comparison to be made today to the situation in Ireland and the situation in Ukraine.
Even historically it doesn't fit. What "invasions" of Ireland are you talking about? Maybe John de Courcey's? In the 12th century without support from the crown?
Please note that I say all of this as someone who would vote tomorrow for a united Ireland without a second thought.
Your comfort with the current NI situation doesn’t prevent historical comparison.