How Many Companies Have Lord of the Rings Rights?

Perhaps the least complicated thing about Lord of the Rings is who actually owns rights to it. It’s pretty much four main entities:
The Tolkien Estate, alongside HarperCollins
Embracer Group, the owner of Middle-earth Enterprises
Warner Bros., through New Line Cinema
Amazon Studios, the film and TV subsidiary of Amazon
What’s confusing is just what each entity can actually do with what they own. Arguably, the people that actually own the Lord of the Rings as a story is the Tolkien Estate—everyone else can just adapt parts of it, and in certain ways.