I do agree, to some extent, and the EU has had their EU digital drivers' license program for ages now. If you finish the courses and score well on the test, you get a certificate that says you can do all the required parts of normal computer operation. That includes creating folders, managing files, doing basic word processing/spreadsheets/email, and a few basic concepts such as "what is a task bar". How much you need to know depends on the level of skill you're trying to prove, but I can tell you that none of them involve installing Linux.
Unfortunately, in offices "being bad at computers" is a funny character quirk and not a reason to send someone on training, but in theory there is exactly such a piece of paper.