Certain programs they run won't work on old operating systems like Windows 7 or 2000 but they work on Windows 10 and Linux. Running an unmaintained old copy of Windows 7 would be pretty bad for someone non-technical because if they decide to ever go-to a questionable site of their choosing, chances are they will get themselves in trouble with a virus / malware.

You can run Xubuntu 20.04 LTS for a few years with unattended updates turned on so they get automated non-UI breaking security patches. Then when it goes EOL upgrade to the next LTS, or even turn on unattended upgrades too with a stipulation that something might change once every few years instead of twice a week. It's a really good environment IMO.

One could have installed mint mate 16 in 2013 and painlessly updated between versions without huge difference between then and now.

Linux isn't a product like windows it's an ecosystem use whatever works for you.

I say this as a sysadmin responsible for maintaining a small fleet, the majority of which are Linux boxes. I've wasted far more hours helping end users with OS-level problems on Windows and, to a lesser extent, macOS. This is in spite of the fact that, again, the majority of the machines I manage run Linux, and all of these users are similar in technical capability.

Give it a try yourself. I'm sure a lot has changed since you last used it. Oh, and make sure you pick something that holds your hand a bit like Manjaro, Pop!_OS, Mint, or EndeavourOS.