While Canonical deserves the criticisms leveled by op (that I agree with), it’s also incorrect to say that they lock security updated behind a paywall.

Anyone that does use Ubuntu gets security updated until they stop supporting that particular release version, which iirc is for six years (I may be wrong, thus is from memory).

I quoted the relevant part and yet you still don't understand that Universe is explicitly not covered by security support by Canonical without Ubuntu Pro.