An example of how to react to UGUI EventSystem select states to get a reactive button

ButtonFocusReactor.cs

using System;
using _project.utilities;
using DG.Tweening;
using Sirenix.OdinInspector;
using TMPro;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using UnityEngine.UI.ProceduralImage;


namespace _project.ui
{
    /// <summary>
    /// Common driver for button animations
    /// </summary>
    public class ButtonFocusReactor : MonoBehaviour
    {
        private bool _isSelectedByEventSystem => EventSystem.current.currentSelectedGameObject == gameObject;
        private bool _isConsideredSelected => _isSelectedByEventSystem || lockAsSelected;
        
        private bool _lastSelectionState;

        public bool canAnimate = true;
        public float selectionTweenLength = 0.25f;
        
        [ReadOnly]
        public bool lockAsSelected; // if unfocused, keep set to the selected view

        // https://assetstore.unity.com/packages/tools/gui/procedural-ui-image-52200
        [Header("Outline")]
        public ProceduralImage outlineGraphic;
        [Space( 10 )]
        public float selectedBorder = 48; // use an enormous stroke to do the fill, rather than go to 0 which "fades out"
        public float unselectedBorder = 2;
        
        [Header("Text")]
        public TextMeshProUGUI text;
        public Graphic icon; // optional
        public Color onSelectedTextColour = Color.white;
        public Color onUnselectedTextColour = Color.white;
        public TMP_FontAsset onSelectedFont;
        public TMP_FontAsset onUnselectedFont;

        private void Reset()
        {
            outlineGraphic = GetComponentInChildren<ProceduralImage>();
            text = GetComponentInChildren<TextMeshProUGUI>();
            icon = GetComponentInChildren<Image>();
        }

        private void Update()
        {
            if ( _lastSelectionState != _isConsideredSelected && canAnimate )
            {
                _lastSelectionState = _isConsideredSelected;
                DoChange( _lastSelectionState );
            }
        }

        protected virtual void DoChange( bool isSelected )
        {
            outlineGraphic.DOKill( true );

            outlineGraphic.DOBorderWidth(
                isSelected ? selectedBorder : unselectedBorder,
                selectionTweenLength );

            text.DOKill( true );

            text.DOColor(
                isSelected
                    ? onSelectedTextColour
                    : onUnselectedTextColour,
                selectionTweenLength );

            if ( onSelectedFont && onUnselectedFont )
                text.font = isSelected ? onSelectedFont : onUnselectedFont;

            if ( icon )
            {
                icon.DOKill( true );

                icon.DOColor(
                    isSelected
                        ? onSelectedTextColour
                        : onUnselectedTextColour,
                    selectionTweenLength );
            }
        }
        
        protected virtual void OnDestroy()
        {
            outlineGraphic.DOKill();
            text.DOKill();
            if(icon)
                icon.DOKill();
            
            canAnimate = false;
            Destroy( gameObject );
        }
    }
}