Linux is actually a great option for elderly people. They have very minimal needs, so they aren't going to run into limitations such as Windows-only software that they absolutely must use. With automatic updates the maintenance burden is minimal, and the risk of malware or viruses is almost non-existent.

You can also ensure that not many things change over time. My parents have been using Linux for over 15 years and they love it. Mate looks basically the same, as do most of the applications they use (file manager, image viewer, Firefox, Thunderbird, etc.). There's no strange software required for their Brother printer/scanner and nothing suddenly appears with each update.