Landscape
How to use Landscape view with iPhone 11?
iPhone SE, iOS 15
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Physically rotate the phone so it's in a horizontal position as explained in the support document you posted from.
Note that the Home Screen will not rotate to landscape but some apps like Safari, Messages and 3rd party Apps the support it will.
If Safari and Messages are not rotating, then check control center, and make sure the rotation lock is not engaged. 