Included in the release notes for macOS Catalina 10.15.5 is the following:
– Major new releases of macOS are no longer hidden when using the softwareupdate(8) command with the –ignore flag
This change also affects macOS Mojave and macOS High Sierra after installing Security Update 2020-003.
For users still running an earlier major macOS version like Mojave or High Sierra, the Software Update pane in System Preferences typically displays a prominent upgrade button for Catalina and a notification badge on the System Preferences icon in the Dock, but until now knowledgeable users have been able to hide those items by using the softwareupdate –ignore “macOS Catalina” command in the Terminal app.
After updating to macOS 10.15.5 or Security Update 2020-003, this command no longer works, with Terminal displaying the following message:
Ignoring software updates is deprecated.
The ability to ignore individual updates will be removed in a future release of macOS.
As documented in a discussion thread in our forums, there are some additional commands that can be used to temporarily remove the notifications, but it’s clear Apple wants as many users as possible to upgrade their Macs with all of the most recent operating system updates.