A few months ago a bough a lenovo thinkpad e480. I tried several linux distros (KDE Neon, Fedora, Ubuntu, Debian, OpenSuse Tumbleweed, now Arch) and all of them had the same problem:
If I plug in my headphone in my jack, the sound doesn't switch to them, but comes from the speakers. I didn't have any luck switching it manually either. With some of the distributions (aso Arch which I am using now) in the beginning everything was working fine, while a few hours ago, I've got the same problem.
(Before trying every distribution I could think of) I also tried all the fixes to the same or similar problems I've found only (except https://www.linuxquestions.org/quest...-a-4175587808/ , as I couldn't toggle the settings suggested).

Here is my alsa-info: http://www.alsa-project.org/db/?f=71...cbbf3268e0d0be

If someone could help me, I would be forever grateful!

Sounds like the hardware to me. I have used several of the distros in your list and I am confident it is not software related.

Did you buy this box new or used?

New. And it works fine on windows. And like I said, sometimes when I do a fresh install it works in the beginning. This time in arch I did't even update anything when it stopped working.

The headphones work correctly in Windows but not Linux? You're saying in Windows, on the same machine, you can plug in the headphones, and it works correctly? But with Linux, on the same machine, you plug in the headphones and the sounds keeps coming out of the speakers? But only sometimes? Other times when you plug the headphones in with Linux, then the sound comes out the headphones?