There was not any Ukrainian nationalism.
There wasn't 'nationalism' as we know it now, the modern nationalism.
But there was some form of Ukrainian self-identity, the country trying to have independence or some kind or real autonomy. The guys like
Bohdan Khmelnytsky,
Ivan Mazepa and some others might confirm that.
...(Ukrainian) peasants did not care either way.
They did care.
May be there was little Ukrainian nationalism but there was definitely a lot of Ukrainian religiosity.
The majority of the Ukrainians were Orthodox Christians, and their religious feeling had been hurt by the Polish Catholics and their Jewish clerks (that's the source of the famous Ukrainian antisemitism of the time). The Russian extortion was probably the same but at least the Russians did not add insult to injury; the Russians were Orthodox themselves, having the same religion was
extremely important those days.
Ye, there was some Ukrainian minority who belonged to
Ukrainian Greek Catholic Church, but the Ukrainian Greek Catholics were considered as 'second rate' Catholics by the 'real' Catholic Poles, so there was less support here. And there were some 'true' Ukrainian Catholics but they were too few.