'Dualism' is very simple: It's the idea (or sense, or feeling) that there's me, and then there's something else outside or me. Something not-me.
Here's me; and then there's you and she and he and them. That's dualism, not some other thing called 'pluralism' or whatever. It's not the many separate things perceived that makes it dualism, but the idea that there's a me 'in here', and something else 'out there'.
Anything advocating a purpose to life, something to be achieved, accomplished or understood, is dualistic.
'I' believe there's 'something' to understand, 'something' to find, 'something' to do; here am 'I', and there is 'something'. That's dualism.
Anything offering judgment or approval is dualistic.
I in here say something out there is good or bad. Again, it's not the 'good' or 'bad' that makes this dualistic; it's the me in here and something out there.
There are many thought systems that claim to be non-dualistic but aren't. Anything offering processes to attainment, or even simple advice, is dualistic.
I'm here as I am right now; and there's some other thing or state or condition that's not yet me or mine but which can become so if I try.
Dualism is understandable. Non-dualism isn't.
Language is dualistic by nature, or at least English is. So's thought, for that matter.