Not sure I remember the source, but even Navalny was not against Russia’s war to get its buffer zones back. Of course, if Navalny was able to magically overthrow Putin, it’d be harder for a democratic regime to fight an offensive war because no one wants to personally participate in a war.
Not sure about downvotes, but Navalny was definitely against bringing back Crimea to Ukraine.
In his own words: "Crimea is not a pastry to pass from hands to hands". After it becomes clear that "3 day" invasion of Ukraine is unsuccessful he changed his mind. But only after it, not before.