Is it normal that desk jobs have turned into 100% screen time?

Abnormal to the nth degree.

Screens have replaced a whole lot of paper moving from place to place, but the nature of office work hasn't really changed.

It's fine to learn a skill that you do outside an office environment, of course, but bear in mind that jobs involving physical labor may also involve increased risk of injury and the possibility that you won't be able to do it as you age. So pick your skill wisely.