How does one constrain rotations of a CharacterController without a Rigidbody?

Hello,

I'm working on a player character and a follower character (the follower follows the player around), based on the 3DBuzz Third Person Character Controller Tutorial. I haven't followed the tutorial myself, but instead I received the files from someone who did.

For the following of the follower I use a simple transform.LookAt() and then use the controller to move the character forward. None of the characters in either my scene or the tutorial files are using a Rigidbody, but in the LookAt of the Follower I tell it to ignore the X rotation of the Player. Like this:

 transform.LookAt(new Vector3(0, otherCharacter.transform.position.y, otherCharacter.transform.position.z);

Now my problem with this is that the Follower will only look to the left, as if it ignores the other axes too. When I tell it to ignore the Y axis, it rotates almost correctly, is able to follow you around just fine, but when the Player's Y-position gets greater than the Follower's, it will still look up and down, which I don't want it to do. Attaching a Rigidbody won't actually do anything, since when I let it use gravity, it'll fall through the floor (even tho it has the CharacterController, and thus a collisionbox), and if I take the gravity out, the constraints won't do anything.

This is the Walk() function I made for the follower, it is called whenever the Follower is indeed the follower (since the player can switch between playing the Player and the Follower)

         void Walk()
         {
             transform.LookAt(new Vector3(0, otherCharacter.transform.position.y, otherCharacter.transform.position.z));
     
             if (Vector3.Distance(transform.position, otherCharacter.transform.position) > 2)
             {
                 follow = true;
             }
             if (Vector3.Distance(transform.position, otherCharacter.transform.position) < 2)
             {
                 follow = false;
             }
     
             //VAxis and HAxis are the equivalent of the Vertical and Horizontal axes called when using the D-pad to control the character.
             if (follow)
             {
                 Controller.VAxis += Time.deltaTime;
             }
             else
             {
                 Controller.VAxis -= Time.deltaTime * 3;
             }
     
             Controller.VAxis = Mathf.Clamp(Controller.VAxis, 0, 0.9f);
         }

So now my question is: How can I fix this?

If there's anything you need from me, just tell me. I hope anyone can help.