Tolkien scholar Tom Shippey, who is supervising the show’s development, told German fansite Deutsche Tolkien that the estate has refused to allow the series to be set during any period other than the Second Age of Middle-earth. This means Amazon’s adaptation will not cross over at all with events from the Third Age, which were dramatised in Peter Jackson’s Oscar-winning trilogy in which the hobbit Frodo Baggins journeys to destroy the One Ring.

Shippey said that Amazon “has a relatively free hand” to add details since Tolkien did not flesh out every detail of the Second Age in his appendices or Unfinished Tales, a collection of stories published posthumously in 1980. But Shippey called it “a bit of a minefield – you have to tread very carefully”, saying that “the Tolkien estate will insist that the main shape of the Second Age is not altered. Sauron invades Eriador, is forced back by a Númenórean expedition, is returns to Númenor. There he corrupts the Númenóreans and seduces them to break the ban of the Valar. All this, the course of history, must remain the same.

“But you can add new characters and ask a lot of questions, like: What has Sauron done in the meantime? Where was he after Morgoth was defeated? Theoretically, Amazon can answer these questions by inventing the answers, since Tolkien did not describe it. But it must not contradict anything which Tolkien did say. That’s what Amazon has to watch out for. It must be canonical, it is impossible to change the boundaries which Tolkien has created. It is necessary to remain ‘Tolkienian’.”

There is this bit in the end though:

Contacted by the Guardian, the Tolkien estate declined to confirm or deny Shippey’s claim.

This new show is about the Second Age of Middle Earth, including the forging of the Rings of Power, the war between Sauron and the Elves of Eregion, Sauron establishing himself in Mordor, the history of Numenor (maybe???) and the War of the Last Alliance which is the opening of the Fellowship film. This is only stuff that appears in the Appendices to the LOTR books.

I believe there is some kind of agreement that the Amazon can't just do a TV remake of Jackson's LOTR or Hobbit trilogy (which would be way better than this show). So they have to do this, which is going to be 95% made up bullshit becuase the Second Age is covered in like 10 pages in Appendix A.