There are 2 repositories under freelook topic.
A script that can be attached to the main camera to rotate and move it in Game Mode (and Build) using simple input.
A script that can be attached to a [Cinemachine Virtual Camera] or the [Main Camera] to rotate and move it in game mode (and build) using the Unity Input System.
Mod with custom freelook system of third person allowing you to move camera 360 degrees while moving in one direction. Supports tunnel vision alike in real life.