Bypass eye dominance
I don’t know what my eye dominance is, but it doesn’t matter because I don’t ‘sight down the saw’. I look at the reflection in the saw-plate and make sure that the board and its reflection are in a straight line, and that means the saw is vertical and you are cutting squarely.
Seeing the line can be done using both eyes providing the line is on the left-hand side of the saw, so if you make sure that your off-cut is to the right, then you can see the line, and cut square every time.
If the line has to be on the right side of the saw then I’ll defer to the suggestion of others: close your left eye and look with your right.