I search unity Cinemachine. And it says Cinemachine is in ‘All Assets’ but there is no ‘All Assets’ option in my package manager. I am using Unity 2019.4.10f1 version. I also search individually in all column but I could not find Cinemachine.
It’s located in the Unity Registry tab. There, you should be able to find Cinemachine just fine. It confused me as well a while ago