SizePerfectCanvas. adapter size.

SizePerfectCanvas.cs

using UnityEngine;
using UnityEngine.UI;

namespace Script.Tools
{
    [RequireComponent(typeof(CanvasScaler))]
    [ExecuteAlways]
    public class SizePerfectCanvas : MonoBehaviour
    {
        [SerializeField] private CanvasScaler canvasScaler;

        private void OnRectTransformDimensionsChange()
        {
            canvasScaler.matchWidthOrHeight = Screen.width * canvasScaler.referenceResolution.y < canvasScaler.referenceResolution.x * Screen.height ? 0f : 1f;
        }
    }
}