You can install facter which is a separate component of puppet. Then you need to manually sign puppet certificate, which is probably quite lots of commends without puppet agent installed actually. Well, it’s complicated.
We are currently in the design phase to do something with it:
On the similar note, I recently started a project called ufacter which aims to complement some of the missing features of the PuppetLabs facter: GitHub - lzap/ufacter: Micro facter - loose implementation of PuppetLabs facter - if you don’t want to install neither puppet nor facter, you could use that. Call that from cron and pipe this into curl to upload the facts. But you still need to have a client X509 certificate accepted by smart proxy HTTPS endpoint. We don’t have instructions to sign certificates manually at the moment. If you are good with openssl command then you can easily have that signed.