Anything involving Nvidia, really.

I installed Xubuntu on an old laptop with a Geforce 635M. During installation I checked "Install proprietary drivers". So it installs the current Nvidia driver instead of the correct legacy one for my GPU, even though it obviously would be able to tell which GPU I have installed.

So then I uninstalled the current one and installed the correct legacy one, but the driver still doesn't work. Took me quite a while that apt remove/install only removes/installs the packages but doesn't actually load/unload the drivers from the kernel.

So I loaded the legacy driver into the kernel, but it still didn't work. Apparently, the current driver takes precedence, even though it doesn't even support the GPU at all.

In the end I had to reinstall the current one, unload both drivers from the kernel, uninstall the current driver and load the legacy driver.

This took me a few hours and I am pretty sure that someone who doesn't have an IT degree would probably just not have a working GPU and that's that.

Then I spent a few hours to get Optimus to run, but couldn't figure it out. So now this laptop cannot be used without a battery source for any decent amount of time, because the GPU is constantly running and consumes massive amounts of energy just to render e.g. a browser window.

Edit: And for sure, anyone who says they have ever had difficulties with anything regarding Linux is directly getting downvotes. That's also a big issue regarding Linux. Whenever someone has trouble or asks for help, there's always some helpful fanboy ready to downvote and call you a noob. Funnily enough, these fanboys usually are running Linux for two weeks so far.