In "The Late Great Planet Earth," Hal Lindsey presents a view of "Armageddon" referred to in Revelation. Is this view considered "valid, and if so, by which Christian groups?" Is Lindsey considered a "false prophet, and if so, by which Christian groups?" Or hasn't a consensus yet formed as to whether or not Lindsey's view "holds up."
It is considered invalid by many Christians. It's also considered valid by many Christians. The closest you'll get to an objective answer is to look at the Amazon book star-reviews, which is what I encourage you to do. It indicates that the book is very polarizing. And I suspect that the answers which will accumulate here will look very much like the written reviews there.
There is absolutely no way to "decide" whether Lindsey's view holds up, so the question is impossible to answer. As you may predict from the book's reviews, you are sure to get quite polarized answers. For example, a random Catholic from the internet says:
And from an article on general subject matter:
From all this we can only assume that mild answers will range from the mild "well, many consider him ok" that Narnian presents, to the mild "read something better" I quoted above.
Questions you may consider asking instead:
It is considered valid by many Christians, specifically those who hold to a pre-tribulation rapture of the Church. Those that disagree with this opinion will generally consider him wrong about this issue, but not a false prophet. Hal Lindsey attempts to interpret Revelation. He certainly is convinced of this interpretation, but that does not make him a false prophet. He still holds to all of the essential doctrines of at least Protestant Christianity--the virgin birth, the Trinity, the death and resurrection of Jesus, etc.
So, he is probably wrong about at least some points and maybe even most or all of them, but he believes in salvation by faith alone in Christ alone--just as many other Protestants do.
By the same token, those who do not believe in a pre-tribulation rapture are not considered to be false prophets by those that do. It's just a disagreement in interpretation, over which we will have eternity to discuss and perhaps laugh about who was right and who was wrong.