When uploading facts from Debian Bullseye (currently testing), the facts are rejected:

# /etc/puppetlabs/puppet/node.rb --push-facts host.example.com
host.example.com: During the fact upload the server responded with: 500 Internal Server Error. Error is ignored and the execution continues.
{
  "error": {"message":"Validation failed: Major version is not a number, Major version Operating System version is required"}
}