Red Hat Developer Subscription for Individuals (16 machines): https://developers.redhat.com/articles/faqs-no-cost-red-hat-enterprise-linux
sudo subscription-manager register
sudo subscription-manager refresh
sudo subscription-manager attach --auto
$ subscription-manager list | grep Status:
Status: Subscribed
Ubuntu Pro for free (5 machines): https://ubuntu.com/pro/beta
sudo pro attach <TOKEN>
$ pro status | grep -A2 "STATUS"
SERVICE ENTITLED STATUS DESCRIPTION
esm-infra yes enabled Expanded Security Maintenance for Infrastructure
livepatch yes enabled Canonical Livepatch service