What we know (or think we know) so far:
1) It's going to be filmed in New Zealand
2) It's not actually going to be "The Lord of the Rings" in the sense that it'll be based on the "Second Age", which is basically a couple thousand years before the events in The Lord of the Rings. Basically the age of Numenor and Sauron's rise, deception, and defeat.
Part of the reason it's set in the Second Age (at least according to Tom Shippey) is that apparently when Amazon purchased the rights, the Tolkien Estate explicitly disallowed any re-telling of the LOTR, and strictly limited any new adaptation to the Second Age. Apparently the thought behind this is that the Estate did not want Amazon to jigger with any plots Tolkien had already created or established. Essentially it's their way of making sure Tolkien's work is kept pure. Because what we know of the Second Age is only the highlights, they are more comfortable with Amazon telling new stories based in Middle-earth, so long as the structure of the Second Age is maintained. So whatever history is already spelled out, it must remain the same, so Amazon has their hands simultaneously tied and yet are free to fully flesh out anything Tolkien did not specifically flesh out.
3) As of now there is a 5 season commitment. It's said the first season is 20 episodes long. It'll be in production for like two years and the thought is it'll be out in 2021.
4) A few actors are reported to have been cast though it seems, due to secrecy, no one is confirming anything.
-Markella Kavenagh (reportedly cast for a character named Tyra)
-Will Poulter (notable for playing Eustace Scrubb, reported to be playing a hero named Beldor)
-Joseph Mawle (reportedly playing a villain named Oren)
-Maxim Baldry (all I can find is that his role is 'significant')
5) Amazon released a map bit by bit before the Second Age stuff was confirmed. It's assumed Numenor will be heavily featured. Nothing earth shattering but it's a pretty map.

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The biggest takeaway for me is how restrictive the Tolkien Estate is in this process. It's crazy to me that Amazon bought the rights to Lord of the Rings only to be able to use material for the Second Age. 1st & 3rd ages off limits. They can't use Silmarillion source material. It can only come from the info found in LOTR. If they have that much control over what is limited, I hope they also have been able to limit certain themes/agendas/content consistency, etc. A woke Middle-earth isn't Middle-earth.
Creatively I think it would be a very fun sandbox to play in. And as a quasi-purist, I think I'll have more fun watching a show like this. It sort of frees you up to not worry about all the changes to the originals.