Errors updating to Cinemachine 2.9.5 on Unity 2021.3.22f1

You don’t need to upgrade all of Unity, just Cinemachine.
You can try with 2.9.7 if you like.
You can still install 2.10.0, despite the lies that the package manager tells you.
Here is how: How do I install a specific version of Cinemachine?