I type this from a 2013 Macbook Air - and it took a lot of struggle today.
There's a pretty big issue with it; Phantom keys.
It took me about 20 minutes today to simply get into my machine because various keys think they're being pressed faster than I could input my password.
It's been doing this for a while now. Starting with 'A' being unresponsive (Probably a disconnect between the electrical circuit) that grew to encouraging S and E to misbehave, and eventually random letters.
One bad apple ruins the bunch indeed.
"But don't you have Karabiner Elements installed? You were concerned about that with Mojave, and you said it worked."
I do!...But it doesn't open and load until the user is loaded, so it does no good for me at the login screen.
So why is this happening?
Simple theory - The battery has swollen over time (Even though it was replaced in Jan. of 2017) and presses the buttons from below.
Either way, it's a problem for someone looking for work. If I can't type properly, we're not getting anywhere.
I probably could sell this (at a huge loss, but that's not my concern right now) and put that money toward a new, far cheaper computer that could handle VirtualBox and various operating systems.