Seems good to me, and a quick test on a stock Kubuntu install gets the updater registering new updates when the system does its own refresh.

This helps for Kubuntu (and Neon ?) users, but what about everyone else?

In D17375#373049, @ngraham wrote:

This helps for Kubuntu (and Neon ?) users, but what about everyone else?

As the code changed here is apt specific, for non apt distro the updater will continue as before to refresh via packagekit 5 mins after system startup, and then afterwards once every 24 hrs.

That's what I thought. Then it doesn't fully fix 401810, since people not using Kubuntu or Neon will still not have a way to change the update frequency.

In D17375#373278, @ngraham wrote:

That's what I thought. Then it doesn't fully fix 401810, since people not using Kubuntu or Neon will still not have a way to change the update frequency.

I don't think this was intended to be a full fix for that in a distro agnostic sense, though it is relevant so posted on that bug. This is specific to apt updates where currently if a x0periodic config files exists then (a) notifier and apt config prompted refreshes will at a minimum double the frequency, and (b) even worse the apt-config setting in days was being misconstrued by the notifier as hours, resulting in even more frequent refreshes. That is what I pointed out and discussed with Aleix a few days ago, which prompted this revision.

This is apt-specific code, so if apt distros are happy with it, then it's as good as it gets.
It could make sense to do the same for other distros, but that's a different battle.

I'll land on 5.14.