How to trigger a Jenkins build on a new artifact in Artifactory?

Now you can use Enable Artifactory trigger in a newer version.

Go to Build Triggers and check the Enable Artifactory trigger checkbox.

More Detail on GitHub Support for Artifactory trigger

It's maybe not as elegant as a hook, but I believe the URLTrigger Plugin will achieve what you're looking for. Listed in their use cases:

This plugin enables users to check if new artifacts (such as binaries) have been deployed in a repository (managed for example by a repository manager such as Sonatype Nexus, JFrog Artifactory, Apache Archiva and so on).

It allows you to check the last modification date and inspect the contents of the response for changes.

You would have to use a polling interval instead of relying on Artifactory to notify Jenkins via a hook, but in my experience polling is relatively innocuous even with lots of polls at high intervals.