I've been wondering whether nationalism is inherently a left-wing or a right-wing ideology.
Historically, the answer doesn't seem obvious. During the French Revolution, nationalism was largely associated with the Left. It challenged monarchy, aristocratic privilege, and the old dynastic order by arguing that sovereignty belonged to the nation rather than to a king. In that context, nationalism was a revolutionary and emancipatory force.
Today, though, the picture seems much more complicated.
In many countries, nationalism is primarily associated with the Right: conservative movements, anti-immigration politics, cultural traditionalism, or ethnic conceptions of the nation. Examples could include much of the contemporary European far right or various forms of right-wing populism.
At the same time, there are clearly left-wing nationalist movements. Irish republicanism is probably one of the best-known examples, where nationalism has often been intertwined with socialism, anti-colonialism, and labor politics. Similar patterns can be found in other anti-colonial or national liberation movements.
What's even more interesting is that the same national movement can contain both right-wing and left-wing currents.
Ukraine seems like a good example. There is an explicitly right-wing nationalist current, represented by groups such as Azov and similar organizations, emphasizing military traditions, conservative values, and ethnic nationalism.
But there is also a distinctly left-leaning current of Ukrainian nationalism, often represented by younger activists and parts of civil society. Their understanding of national identity is frequently combined with feminism, LGBTQ rights, decolonial theory, and other progressive ideas. Ukrainian feminism, for example, draws on a long tradition of influential women writers and intellectuals, while decolonial studies have become increasingly important in interpreting Ukraine's relationship with the Russian Empire and the Soviet Union.
Am I missing something here, or is nationalism better understood as a politically neutral framework that can be adopted by both the left and the right?
Ukraine is a difficult example, and I think we can safely say that the Soviet approach didn't work, and that's a key example that we can look at when evaluating the theory.
Like you said, Lenin's approach in practice wasn't consistent with his theoretical arguments. The approach was supposed to be a compromise between those concerns, as well as strategic concerns (the risk of divide and conquer) and political concerns (different factions calling for different things). But whatever his intents or justifications, the fact that Ukraine is such a mess today says that something went wrong in a big way.
It's easy to say that Ukraine should have just been given full independence, and that's probably correct, but we also don't know for sure what would've happened. What implications would that have had for WWII? Perhaps the strategic difficulties would have been offset by presenting a better image to other countries and getting more support.
Applying the theory to the present conflict gets even messier. In theory, Ukraine being independent would be a good thing, but in the current conflict it's really more about which sphere of influence it's in. The question of what to do when there's a secesionist movement within a nation that's not fully developed is particularly thorny. I really can't see any way things could work out for that region, unfortunately, so my stance is just to leave it alone.
In general, it's an enormously difficult and complex question, especially in practice, and the best we can do is to try to establish basic guidelines in the abstract, while looking at each situation case-by-case.