A previous question focused on whether link-only answers that contribute something helpful, but not an actual solution, should be converted to a comment. My question here is whether certain kinds of link-only answers would generally be considered an acceptable answer as-is.
Situation: The link is to a good tutorial that answers the question (say a video or extensive pictures that explain something that is difficult to explain without them). Trying to extract the essential information would be impractical and would eliminate the value/benefits of the tutorial, which was the purpose for posting the link.
Situation: The question is too broad ("good answers would be too long for this format"). Someone posts a link-only answer before the question is closed (or the question is never closed), and the link is a treatise on the subject, which is what is required to answer the question; way too long to paste or extract the essential information.
Same situation as above, but the link is simply overkill for an on-topic question.
At some point, the link may break and the answer will be useless. In the meantime, we're sending the reader somewhere else for the actual answer.
I assume that deletion would not be desirable in these cases because helpful information would be lost. So if action is appropriate, it would be moving the link to a comment or downvoting the answer. In this case, downvoting isn't useful; it's not practical to improve the answer so it would just cast doubt on the content.
Should anything be done with these kinds of answers, or are they considered acceptable as-is?
If action is appropriate, might flagging these (or other link-only posts), result in a declined flag?
The issue with most link-only posts is answer quality, which flags are not supposed to be used for. The previous question explored whether there was an element of "not an answer" (should be a comment, instead), which would have been a basis for a flag.
Based on Random's comment, below, I'll assume that if flagging is appropriate, it should be a custom flag with an explanation. However, is flagging "universally recognized" as the recommended action here, or might the flag being declined depend on which moderator handles the flag and/or other factors?