Linux

That really depends on your needs, and the Linux distro you're using. Generally speaking, the greater your requirements (and therefore usage), the more finicky an OS gets.

I switched my non-techy Mum and Dad over to Linux over a decade ago (Xubuntu previously, now Zorin) and in all this time, I can count on one hand the number of times they called about an issue. The entire motivation to switch them over was because Windows was so unstable and would either tend to break after an update, or get infected by malware or something, and I got tired of being the IT guy for them and having to constantly fix it. I reasoned that Linux would be a good candidate for them because they have very simple requirements - they mainly just use a browser foe the most part, work with documents occasionally and do a printout once in a while, like for flight tickets and stuff. More than a decade later, my reasoning was proven right, and I'm glad it's been working so well. Linux was the very definition of "just working", at least for my parents.