How and where to switch on this option?
It's in the FAQ somewhere.
You can code your Phaeton for different regions.
I don't remember how the thread is titled. Maybe "regions" or" European coding" something similar.
In the U.S. they are coded to come on when you turn the ignition on and are used as DRLs and for the distance being measured in miles.
Canada invented DRLs so the headlights come on for Canadian coding also but they use Kilometers.
The lights on my Ford don't come on unless I want them on but I usually drive with my lights on for safety.