The only ads I notice is that apt shows how many packages can be updated through an optional paid Expanded Security Maintenance. This isn’t very obtrusive but I’m on a 4 year old LTS release currently so things might have changed.

Receiving updates for anything in Universe requires Ubuntu Pro which is free for home users but still requires signing up to give you access to that update repository and once you sign up, they can match your account with what you install/update, so there is server-side tracking. In theory there is the possibility of community-maintained updates there but that required adhering to Canonical's draconian version freeze rules. Something Fedora and its derivates do not have to that degree (during a release cycle any update is fine if it doesn't break compatibility).