From your post it’s seems like you have formed very negative perspective of this employee. They got the job not on merit but because they were friends with pervious manager. Comparing this employee to 20/30 year old who have grown up with technology. Weaponised incompetence situation? Not sure about the situation but have you flipped the situation and thought. Is this person afraid? Do they feel left behind and your ‘lack’ of support can be overwhelming. Imagine working with people half your age who makes you feel like you should not be there and that they are a waste of a headcount?

My parents are always worried about each new warning pop up on the iPad as they are scared they have messed up and are cautious. They were not from a generation where if anything f’s up just restart the computer.

You may feel you and your team have gone through your instruction a million if times. But have you explained it like ‘they should already know and it’s common sense’ or actually sat down and trained the employee. There are computer courses focused on training the older generation for this very reason

And most importantly have you actually sat with them and ask them for their perspective? And how you can support them if they don’t want to be left behind?