With v0.10.2, you can create S3 buckets with notifications like this:

new sst.Bucket(this, "Bucket", {
  notifications: ["src/lambda.main"],
});

More examples here https://docs.serverless-stack.com/constructs/Bucket

BTW this is what they released yesterday (?) https://aws.amazon.com/blogs/aws/introducing-amazon-s3-object-lambda-use-your-code-to-process-data-as-it-is-being-retrieved-from-s3/

Oh no..

notifications

are just adding/removing objects in S3 bucket triggering Lambda function