So, they’ve likely had to figure out what rules will need to be followed according to the area where they film (which is about 40 miles west of London), not to mention any safety measures set about for television and movie sets in general.
As we all know well by now, social distancing and the wearing of masks have been requirements for moving about the world safely for several months.
While those who work behind the scenes on The Witcher and other productions can still take those precautions, these are things that can’t really be done on camera and have filming go about as usual.