kubuntu desktop switching via keyboard stopped working

My system:
Kubuntu 18.04 fully up to date as of 01/01/2019 on an old laptop that ran Ubuntu 14.04 with no hiccups whatsoever.

I don't use activities.
I have a 3x2 grid of desktops with the following shortcuts.

Ctrl+Alt+Arrow to switch desktops - these recently stopped working.
Ctrl+Alt+Shift+Arrow to move a window to another desktop - these still work fine.

I have tried changing the shortcuts for switching desktops, nothing works. The desktops widget still lets me change desktops by mouse click.

The commands "wmctrl -s number" and "qdbus org.kde.KWin /KWin setCurrentDesktop 1" still work, so I made myself a script and added some custom shortcuts, but it is sad that I should have to.