Linux

Depends on just how illiterate imo.

Here's a good usecase:

My mum is completely tech illiterate, I have to teach her how to every task individually, and she has to write them down and follow them step my step. Tasks like emailing a document are a challenge. Linux is great for her. She isn't used to windows anyway, and Linux makes it harder for her to accidentally make damaging changes, collect viruses or experience unexpected ui updates. It has much less maintaince, so it's a lot less work for me to manage the system.

Here's a bad usecase:

You are a user who can do the basics of using a website, install new apps, use usb drives etc etc. You are used to windows ui like where to find apps, where the close button is etc. You dont have a tech friend set up your stuff but if something goes wrong you are boned. This isn't a good use unless you are interesting in becoming more tech literate (its easier to learn, if you can google your problems).