Yeah... thanks - there was a program called Dimmer that worked great! I might be able to only use it when watching videos or something.
It's a Windows-only program and I can't get it to work correctly on this OS. It will work great on a window that I don't have to click on or interact with, though, since (with it's limited usability, being patched together via Wine) it works by putting an un-interactable overlay over the screen that dims past the 0%.