According to what I've read the Note 20 does not seem to have the option to change screen resolution.
A similar thread elsewhere … reddit.com/r/samsung/comments/idpvuu/how_to_change_the_screen_resolution_on_note20.
Daily Driver > Samsung Galaxy s²³ Ultra 512Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "