SK probably wouldn't mind receiving some NK refugees, to make for their ~0.7 fertility rates.
Iraq, Libya or Lebanon don't have that advantage (and Kiev would get that advantage only if switches to being pro-Russian).
Aside from either, how many nuclear states have been invaded in the past 80 years? Apart from Ukraine's incursion into Russia's Kursk oblast last summer, the answer is a big fat zero. Finally (and this also applies to my post), social media is the worst place for any foreign policy discussion because it offers asymmetric returns to a foreign actor attempting to subvert a country's policy who happens to speak the country's language, and English is a very popular international language spoken by many people abroad at this point in history.
The answer is Israel was subject to a full-scale invasion in 1973, despite having nuclear weapons since 1966. There have been regular border skirmishes between India and Pakistan since long after they both went nuclear. We also have Argentina's seizure of the Falkland Islands in 1982.
None of the conflicts between India and Pakistan since either of the powers got Nuclear weapons (1974 and 1998, respectively) could be reasonably characterized as invasions.
The Falkland islands are a British overseas territory. They are self governing, but the UK is responsible for their defense and foreing affairs. Classic protectorate. Obviously invading the Falklands is very different from invading the UK.
I guess you could look at their non-admission as evidence to the contrary, but it's not like they're selling enriched uranium as a souvenir to tourists at Ben Gurion international.
Further, while it was widely suspected Israel had a nuclear weapons program, that's a very different thing than having a bomb. Iran is believed to have had a nuclear weapons program. So have many countries.
Sure, but I don't think you understand what goes into keeping nuclear weapons ready. Even assuming Ukraine can manufacture the complete supply chain required for ICBMs, they still have to make and maintain their own warheads. That means either refining nuclear material domestically (where it will get destroyed at any cost by Russia) or importing it from an ally a-la the United States who has no desire to deal with the consequences of that. Ukraine is a strong country, but they cannot sabre-rattle the way Russia can.
Also, I don't think you can cherry-pick Mearsheimer so easily. Even in Ukrainian Nuclear Deterrent we see him discounting NATO as an impotent defense, an assumption that that very much isn't true today and one that he (somehow) still seems to believe in. I think his essay is showing it's age, and then some.
Great Britain was, in 1982 (the Falklands War). It that such a fat zero?
How? Are you saying the median person in any of those making an informed decision would swap places with a random person in North Korea?