Oh, one ought not to underestimate Ukrainian consciousness. It was pretty much entirely middle-class, but then so was Russian nationalism is the modern sense. There was an older, more visceral faith-and-soil "Russianness" (which the Ukrainians and certainly the Belarussians generally felt as well) but although the middle-class nationalism of Russia drew actively on it in its mythology they weren't the same thing. There was a strata of in Ukraine who often strongly felt themselves to be Ukrainian: village schoolmasters, journalists like Petlyura, the sort of people who'd been drafted into the Russian army as subalterns and NCOs, really.
Until it actually happened, of course, very few of these nationalists would have considered separating Ukraine from a federal Russia altogether. They wanted a government that would promote Ukrainian language and culture and be part of a Russian Empire reformed into a federation of different countries. Which is what happened, actually!
(I joke, but Hrushevski was welcomed back to Soviet Ukraine in the 20s and there were many like him.)
Belarus, of course, had very little middle-class that wasn't Jewish, no tradition of statehood, no universities, etcetera and the Belarussian nationalists really were just a circle of academics at the University of Petrograd. The Belarussian peasants were incredulously explaining to the authorities that they spoke only Russian in fluent Belarussian well into the 1920s.