I don’t run Ubuntu, but was surprised I’d not heard of this.

This is canonical trying to make money for security updates, and stopping companies just running it for free, instead of using a licence (my own take). They are following a model by IBM, apparently.

You can get round it by getting a ‘pro’ licence for free for up to 5 machines. At least according to ask Ubuntu. https://askubuntu.com/questions/1452299/im-getting-the-message-the-following-security-updates-require-ubuntu-pro-with

More reasons to avoid Ubuntu, imo.