You’re correct that international law does not consider an ethnic conflict on a border as a justification for an invasion, but what did I say that is not true? The voting in the Ukrainian election in 2014 was largely along ethnic/linguistic lines and a pro-Russian politician from Donetsk, a guy named Yanukovych, was elected. Kyiv, the capitol, is an extremely pro-western area of Ukraine and the locals really didn’t like Yanukovych and rioted, with a significant number of neo-Nazis participating in the riots, driving Yanukovych out of office. His replacement was installed by a procedure not found in Ukraine’s constitution and was from the faction that had narrowly lost the previous election. Donetsk, where Yanukovych is from, Luhansk, and the Crimea, all areas with a majority of ethnic Russians and which had supported Yanukovych refused to recognize the new government and either voted to join Russia (the Crimea) or declare independence (Donetsk and Luhansk). Fighting started shortly after that, with armed para-militaries attacking the separatist areas. How is that not an ethnic conflict?
Svoboda, the extreme right neo-Nazi party has as a statement of its goals, the “de-Russification” of Ukraine. They blocked the peace deal that was negotiated in 2015 (the Minsk agreement) because it would have recognized Russian as a second official language and given the eastern, heavily Russian areas of the country a status similar to Quebec’s with relation to Canada. I think that when major players in a conflict have removing recognition of another ethnicity as a major goal, that the fighting is properly called an ethnic conflict.
I do think there’s a smokescreen covering what is going on over there. The absolute intolerance for ANY dissenting views or facts has obscured most of the history and background. Stating things that are objectively true, like countries representing 2/3 of the world’s population are neutral or pro-Russian has gotten me accused of being a trolley. In other forums I have been personally attacked for pointing out that gallup did a poll in Crimea after it joined Russian and found overwhelming support for that move or for listing the easily googled percentage of ethnic Russians in Donetsk and Luhansk (surprise! they’re the majority of the population there.) Prior to the invasion, there was no partisan line on any of the events going on in Ukraine, so whatever political bent you have, you can easily find a source you trust that will confirm everything I’ve said, but very few people reading this will take the effort to move their mouse and type a couple of words into a search bar. They will, however, type more characters to attack me for disagreeing with the party line. That’s actually sadder and scarier than anything going on in Ukraine right now.