When does linux not "just works"? I have been running linux on my thinkpads (x200, x220, w540, T470, T480s) etc and "it just works", with appreciably much less fiddling around than I would on a similar windows desktop with drivers etc. (My last install of linuxmint on my T480s I think I spent more time fiddling with vimrc than the actual OS).
And I dare say that on servers, linux certainly "just works".
The answer to this is "For almost its entire history of being used as a desktop operating system by users without a significantly above average level of technical knowledge."
I think Linux is in a pretty good state for at least the last few years but you have to be either unreasonably lucky or simply joking to be able to pretend you are unfamiliar with the concept of running into various hardware/driver/software issues attempting to run Linux as a desktop OS. Even if you stick to "Linux Certified" hardware like Thinkpads.
Linux is my OS of choice these days, but over the years I've had 10x as many issues as I have with my Windows systems and I probably have 10x as much time in raw hours using Windows.
I think perhaps something happens to those of us with experience and expertise is when we run into an issue we might know how to fix it in 30 seconds or a few minutes so it doesn't even seem like it was an issue to us, simply part of configuring the system. However, when it happens to someone that's not experienced that same "non-issue" might result in them spending 4 hours on forums and various websites trying to figure out how to do something that would only take a few seconds if they already knew how.
That's assuming they don't just throw their hands up immediately and ask someone to fix it for them.
1. Hibernation is broken in three different ways (1. it's disabled by default 2. it resumes instantly when certain hardware is plugged in 3. it only works if almost no programs run, probably because the default swap partition is too small)
2. Computer freezes when running out of memory. Still not sure how to improve this, perhaps a bigger swap partition, perhaps changing the OOM killer configuration or installing another OOM killer daemon.
3. Ran out of space on the boot partition so kernel updates won't work until I figure out how to manually fix that. Plus the last kernel it installed before complaining doesn't boot at all, so I have to manually pick an old one.
And my earlier attempts on other distributions didn't go better either. Fedora managed to corrupt its package manager state and started complaining about incorrectly signed packages. And on Ubuntu I didn't manage to switch to nvidia's driver, it kept using nouveau with no indication of what's wrong.
And I dare say that on servers, linux certainly "just works".