You can already see how it strengthened their national identity — I'm reading/listening to a lot of both personal and professional accounts on the matter and people of the Russian-speaking regions specifically (most notably Kharkiv and Odessa) talk about how the war gave them a previously almost non-existent feeling of unity with people from the Western regions like Lviv and Zakarpattia. Russian language also seems to be getting gradually displaced even in cities like Odessa where talking in Ukrainian pre-2014 was seen as a huge oddity (if not to signify a certain nationalistic intent — not my words). Now everyone who can (and most Russian-speaking Ukrainians can) speak Ukrainian, prefers to use it instead of Russian for obvious reasons.
Even going by some instagram accounts that I follow, it had been an interesting change — I think only 2 Ukrainian accounts out of all that I follow that posted in Russian before the war continue to post in Russian up until this day and one of those (Alexander Rodnyansky Sr.) does it because he specifically targets Russian audience, trying to give them an alternative version of events. The rest had switched to Ukrainian.
The tragic thing is that I don't see how Russian-Ukrainian relations can realistically improve/get back to normal (even if it's a relative normality) in decades to come. The entire mythos of modern Ukraine will be based on a (hopefully) victory over Russia in their war for independence — and rightly so.
