That question is practically a case study in answer flagging; I killed all three answers on it. There was one that offered a solution if you're using Pulseaudio; I would've left it except you commented that you weren't. I edited that into the question, which made the answer inapplicable, so I converted it to a comment (I probably could've just deleted it, but it at least led to an edit). Another asked a couple clarifying questions without any "and here's how you fix it", so I converted it to a comment as well. The third (which you linked to) offered a workaround you already mentioned in the question, so I just deleted it
So in short, yes, you can flag answers that don't actually address the question, or don't offer any solutions. However -- and people get this wrong on other SE sites constantly -- you can't flag answers for just being wrong
Example question: How do I list the files in a directory?
Answer 1: You can list files with the
Answer 2: You can remove files with the
Answer 3: Which distro are you using?
Answer 1 is wrong, but tries to answer the question, so you should downvote (and maybe toss in an "uh, no, that deletes stuff" comment). Answer 2 is answering completely the wrong question, so you should flag it as a non-answer. Answer 3 isn't an answer at all, so you should flag it as a non-answer and we'll convert it to a comment on the question