It appears curved to us because we mathematically transformed the reference frame.
If you are allowed to transform your geometric space to say “no straight lines” then there are no straight lines in math either. Because you could perform a transform on the straight line into a curved geometry.
Neutrinos travel in a straight line.
Unfortunately (fortunately?) the space they’re traveling through is curved. It was a good attempt though neutrinos.
The neutrino neither knows that nor does it care about it.
In it’s reality, the line remains perfectly straight.
It appears curved to us because we mathematically transformed the reference frame.
If you are allowed to transform your geometric space to say “no straight lines” then there are no straight lines in math either. Because you could perform a transform on the straight line into a curved geometry.
I’m with you, I was mostly joking. This whole question just hinges on definitions of “straight line” and “flat plane” anyways.