CharacterController jump:

if (controller.isGrounded &&
    jumpAction.action.WasPressedThisFrame())
{
    verticalVelocity = Mathf.Sqrt(
        jumpHeight * -2f * gravity
    );
}

Rigidbody jump:

if (isGrounded &&
    jumpAction.action.WasPressedThisFrame())
{
    rb.AddForce(
        Vector3.up * jumpForce,
        ForceMode.Impulse
    );
}

Useful polish techniques:

• Coyote Time
• Jump Buffer
• variable jump height