A Linux computer for my grandma. The correct tech answer when doing things for regular people is standard tech that lots of people use.
A non-expert trying to use Windows on the internet in three early 2000s had a near 100% chance of filling it with malware.
Now I have a couple Windows installs that have been going strong for years. One of 'em has shady proprietary Chinese factory flashing tools on it, and a full development environment for TI graphing calculators. That was my old computer; I don't use either of those tools anymore so my new computer doesn't have them.