ProjectileMortar.cs

[SerializeField] private AnimationCurve curveHeight;
[SerializeField] private float curveMaxHeight;

public Vector3 Move(Projectile projectile)
{
    // move towards the target in an arc, taking a constant amount of time
    var linearT = projectile.CurrentTime / Duration;
    // we have to move XZ and Y separately so they dont fight each other
    var movePosition = Vector3.Lerp(projectile.StartPosition.PositionXZ(), projectile.TargetPosition.PositionXZ(), linearT);
    // in case the start and end Y values are different (which they should be since the turret is higher)
    var baseY = Mathf.Lerp(projectile.StartPosition.y, projectile.TargetPosition.y, linearT);
    // use the animation curve (upside down parabola) to find the magnitude of the Y change
    var arc = curveMaxHeight * curveHeight.Evaluate(linearT);
    // finally, add it all together
    movePosition.y = baseY + arc;
    return movePosition;
}