Simple Udon scripts for changing ligthmaps at runtime

LightMapHolder.cs

using UdonSharp;
using UnityEngine;

namespace TKMNY
{
    [UdonBehaviourSyncMode(BehaviourSyncMode.NoVariableSync)]
    public sealed class LightMapHolder : UdonSharpBehaviour
    {
        [SerializeField] Texture[] lightmaps;

        Renderer[] renderers;
        MaterialPropertyBlock block;

        void Start()
        {
            block = new MaterialPropertyBlock();
        }

        public void Initialize(LightMapManager lightMapManager)
        {
            renderers = lightMapManager.GetRenderers();
        }

        public void Apply()
        {
            foreach (var renderer in renderers)
            {
                var index = renderer.lightmapIndex;
                if (index < 0) continue;
                renderer.GetPropertyBlock(block);
                block.SetTexture("unity_Lightmap", lightmaps[index]);
                renderer.SetPropertyBlock(block);
            }
        }
    }
}

LightMapManager.cs

using UdonSharp;
using UnityEngine;
using VRC.SDKBase;

namespace TKMNY
{
    [UdonBehaviourSyncMode(BehaviourSyncMode.Manual)]
    public sealed class LightMapManager : UdonSharpBehaviour
    {
        [SerializeField] LightMapHolder[] lightMapHolders;
        [SerializeField] LightMapTrigger[] lightMapTriggers;
        [SerializeField] Renderer[] renderers;

        [SerializeField, UdonSynced, FieldChangeCallback(nameof(SyncedIndex))]
        int syncedIndex;

        public Renderer[] GetRenderers()
        {
            return renderers;
        }

        public int SyncedIndex
        {
            get => syncedIndex;
            set
            {
                UpdateLightMaps(value);
                syncedIndex = value;
            }
        }

        void Start()
        {
            foreach (var lightMapHolder in lightMapHolders)
            {
                lightMapHolder.Initialize(this);
            }

            for (var i = 0; i < lightMapTriggers.Length; i++)
            {
                lightMapTriggers[i].Initialize(this, i);
            }

            UpdateLightMaps(syncedIndex);
        }

        public void SetIndex(int i)
        {
            Networking.SetOwner(Networking.LocalPlayer, gameObject);
            SyncedIndex = i;
            RequestSerialization();
        }

        void UpdateLightMaps(int index)
        {
            for (var i = 0; i < lightMapHolders.Length; i++)
            {
                if (i == index)
                {
                    lightMapHolders[i].Apply();
                    break;
                }
            }
        }
    }
}

LightMapTrigger.cs

using UdonSharp;

namespace TKMNY
{
    [UdonBehaviourSyncMode(BehaviourSyncMode.NoVariableSync)]
    public sealed class LightMapTrigger : UdonSharpBehaviour
    {
        LightMapManager lightMapManager;
        int index;

        public void Initialize(LightMapManager lightMapManager, int index)
        {
            this.lightMapManager = lightMapManager;
            this.index = index;
        }

        public override void Interact()
        {
            lightMapManager.SetIndex(index);
        }
    }
}