Three of those on your list are far from true. Ukrainians are closer to Russians (as they all came from the Kiev Rus, Rurik dynasty) then Irish are to Ulster-Scots/Anglo-Saxons. Ulster-Scots/Anglo-Saxons came to Ireland as part of colonization of Ireland (Plantations of Ireland). You can tell a Ulster-Scot from an Irish person as they live in separate communities, support different things, and go to different churches (mostly).
Actually, nothren Ireland and eastern Ukraine are very similar. The fact that Ukrainians and Russians were arguably one people 900 years ago does not mean they are close today. As for colonization, many Russians migrated to Donbass for industrial work starting in the 1890s. This migration continued through the communist era as industrialization expanded. So, like the ulster scots, there is a community that has resided in an area for generations, but is arguably not native.
You can tell a Ulster-Scot from an Irish person as they live in separate communities, support different things, and go to different churches (mostly).
No, you cannot always tell Ulster Scot from Irish physically or by interests. There was alot of mistaken identity killings on both sides.
Likewise, you cant tell "Ukrainian" from "Russian" physically, nor is always easy to tell who is speaking "Russian" verse eastern Ukrainian dialect. Like the Ulster scots and Irish, there are seperate interests- but only to a degree.
Seperate Churches? Most western Ukrainians are Greek Catholic, or Ukrainian Orthodox (Kiev Patriachate). Eastern Ukrainians tend to be Ukrainian Orthodox (Moscow Patriarchate), ethnic Russians tend to be Russian Orthodox.
Seperate communites? Not so much, though there are towns and villages that are strongly ethnic Russian or ethnic Ukrainian. This may actually help as people need to live with their neighbors.
No such thing as experts consultants on Northern Ireland. The "peace process" is in it's early stages with acts of violence still happening. It's also not a process that can be done easily without the right circumstances.
Things are not perfect in northeren Ireland? I believe you. And, yes, things are not going to be perfect in eastern Ukraine anytime soon. The goal, howevber, is not perfection. Rather, the goal is no continuos car bombs / grad exchanges. Likewise, I bet the northeren Irish can give some advise on generating the right circumstances.
Then there is nobody in Ukraine who has the respect of both extreme factions like Northern Ireland had John Hume with the help of David Trimble. Also there is no 3rd party (Nation) that can step in from a neutral role like the US did in Northern Ireland peace process.
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Hopefully, those people can be cultivated. Good point about the no 3rd nation though. That is porbably the only valid point.