If your solution to malware problems with an unsophisticated user is to just cripple their ability to install anything, why not let instead let them keep Windows/Mac and give them an account with minimal privileges?
There are several ways switching an unsophisticated user reduces this problem:
- Ads for malware-laden $RANDOM_SOFTWARE downloads aren't targeted at Linux desktops in the first place.
- The ads that mimic UI widgets don't match anything in the desktop UI, making them much easier for unsophisticated users to identify as suspect.
- Saying that $RANDOM_SOFTWARE they want to install isn't Linux-compatible (which admittedly does generate moderate pressure to switch back) is usually a more acceptable answer than "No, I won't install that malware-riddled piece of crap for you", however gently worded.
I switched over my father-in-law's laptop to Chromium OS for this exact reason.
(mostly) automatic updates.
no malware.
zero configuration to allow for breaking anything.
no "can I install XX?" questions. The answer is always "if it's in the chrome store".
A good browser does everything he needs.
Very quickly most will get the idea that the computer is broken and you need to come and fix it because you were the one that broke it.
FYI, since a few years, TurboTax has an online version that I use on Linux.