As an example: see this answer. As explained in the comment by JRE, it answers a different question ("how do you measure voltage with a multimeter") than the one asked ("how can and Arduino measure its own supply voltage").
I was about to flag it as "Not An Answer", since, well, it is not an answer to the question asked (moreover, in this specific case, it is a copypasta from somewhere else without attribution, and an unreadable wall of text - but let's ignore that for my concern).
Before doing so, I checked if there was an existing policy on these cases. I didn't find anything on our meta here, but I found this on the main meta: When an answer answers the wrong question, is it Not An Answer?. Well, I was suprised to see that the two answers there seem to indicate that this should not be flagged.
Shall we conform to this, here on EE.SE? Shall we leave such answers and simply downvote them if we feel like it? Or should it be flagged and deleted?