Comment by ndiddy

Further context: Ubuntu Pro is an extended support subscription for Ubuntu. Previously, Canonical would only provide security updates for packages in the "main" repo, while packages in the "universe" repo were solely updated by community package maintainers. It looks like subscribing to Pro will grant access to a new stream of security updates by Canonical for the "universe" repo, while not subscribing will leave you in the same state you were previously. It seems like the main problem here is Canonical completely messing up how they're communicating this to users (also, I would be pissed off if I kept seeing the nag messages every time I checked for package updates).