Off the top of my head things that Ive run into over the years that would have caused 99% of computer users to throw Linux in the bin:

*Having to edit xorg.conf to set the graphics driver

*A typo in the sources list that prevented any packages from downloading (distro upgrade)

*A bug in systemd that resulted in the OS not booting (fresh install)

*The wrong graphics card driver being selected and not being installed correctly because Ubuntu kept back 5 packages necessary for it to function (fresh install)

*A bug in how Ubuntu handles the disk platter that causes hard drives to fail far more rapidly than they should (that bug has been there for years and probably ruined a few hard drives)

*Having to recompile the wifi driver after every upgrade (broadcomm chipset) before the driver was included in the kernel and having to reinstall the OS after the driver was included in the kernel because something went wrong during the upgrade. ie recompiling didnt fix anything and the native driver wasnt working either.

*failed drive encryption

*grub being installed incorrectly (no boot)

*dealing with UEFI to maintain a dual boot for programs that cannot be emulated or virtualized effectively (lag sensitive non-native games)

*Audio output defaults being incorrect (no sound, no mic)

But the one thing that above all else, will drive newbies away is how the general linux community tends to respond to things.