I ran into an issue after installing Kubuntu 19.10 where the driver manager would no longer show me which hardware devices were awaiting configuration. This problem only occurred after changing the default font size across all of KDE.
Some digging led to this StackOverflow post,
where pubalapoub suggests running
sudo update-apt-xapian-index. A
mere 30 seconds later the driver manager was again functioning, and I
was back in business.