A friendly heads-up: I think you mean “Liberation Serif”. Serif and sans-serif (“without serif”) are common categories for fonts.

Man pages are the only reference material I know that has more information-free circular definition chains than Wikipedia. And I imagine that it’s for much the same reason; they’re primarily written and fought over by experts who only need terse reminder notes for themselves, and who can’t remember what it was like not spending every day up to their elbows in the subject.

I have a stupid question: Are you sure you’re not confusing “line out” and “headphone out”? They’re different, and pretty much every desktop supports both these days. But standard PC speakers usually connect to the “headphone” socket.