From Phasing of Stable Release Updates
For some time we’ve wanted to phase, gradually roll out, updates to expanding subsets of Ubuntu users so that we may monitor for regressions and stop the update process if there are any. The support for phased updates has existed in update-manager for a while, ...
I added the emphasis.
I'm bringing this up because of a recent Q&A dealing with a kernel update being yanked: Why did Bionic kernel update to 4.15.0-24 get removed from the repos?. The accepted answer has this:
Note that this bug was critical, and worthy of pulling because booting at GRUB from previous kernels wasn't a viable workaround. Some folks reporting had to reinstall to restore functionality.
From the comments there, it seems that users of GDM were affected. Users of LightDM weren't. I got the kernel update before it was yanked and had no problems (that I know of) possibly because SDDM, Kubuntu's display manager, isn't affected as well?
Anyway, the question I linked to and another question posted earlier also by Organic Marble, Strategy to deal with Canonical's increasingly poor QA?, makes me wonder if Plasma Discover or Muon or Synaptic are covered by phased updates thereby offering some probability of protection versus updating via the command line.
Brian Murray's response (on 12 Aug 2013 at 10:44 am) to a question in his blog has:
@vrm – I’m not aware of how much of the update-manager code base KDE uses. It’d be best to check with a KDE developer.
Since that's way back from 2013, I wonder if there's any clarity now.