Lightsail bucket now support CORS configuration through AWS CLI:

To configure CORS for a bucket using the AWS CLI

1. Create a JSON file containing your CORS configuration. For example, create a file named cors-config.json with the following content:

   {
     "CORSRules": [
       {
         "AllowedOrigins": ["https://example.com"],
         "AllowedMethods": ["GET", "PUT", "POST"],
         "AllowedHeaders": ["*"],
         "MaxAgeSeconds": 3000
       }
     ]
   }
   
   

2. Use the AWS CLI to apply the CORS configuration to your bucket:

   aws lightsail update-bucket --bucket-name amzn-s3-demo-bucket --cors file://cors-config.json

3. Verify the CORS configuration was applied successfully:

   aws lightsail get-buckets --bucket-name amzn-s3-demo-bucket --include-cors

please refer to: https://docs.aws.amazon.com/en_us/lightsail/latest/userguide/configure-cors.html