Now that I think of it, there have been two times relatively recently that I've not had something work "out of the box".

One is for a WiFi dongle: it needed a driver that wasn't in the non-free-firmware package, and the manufacturer's Linux driver was too old to work with modern Linux. Fortunately, someone had written a replacement driver that I could get from github. That involved compiling the driver code, though, and the process wasn't something a non-geek could be expected to do.

The other wasn't for a laptop at all, but a tower. I'd installed a WiFi card in it that didn't work out of the box -- I had to copy the firmware from the CD that came with it onto my machine to make it work. That was easy enough to do, though, that my grandma could have done it without a problem by following the readme on the CD.

That said, I run an abnormal number of Linux machines, and two hiccups out of a dozen or so seems like a decent track record to me.