You aren't hallucinating: there is a tree outside.
Science studies the same tree that you see out your window... observation is part of the scientific method...
Are you really trying to argue that nothing you perceive is real? That's your argument?
It's a ridiculous argument and a waste of time.
If reality were a computer simulation there wouldn't be any "objective reality" for science to study anyway..
I don't think we can take this much further. There's nowhere to go from here.
Have a nice day