I am currently running Kubuntu 16.04 with a recent update that is using Plasma version 5.5.5. I know that it is an older version but it is part of the LTS for 16.04. Not sure how/where to report this. With a recent package update (not sure which one caused it), the scroll wheel stopped working on the digital clock applet that is in the panel. Previously it scrolled thru the selected timezones for the clock and updated the time as well for the named timezone. If you hover over the clock it does show the times for the various timezones, but that is not want I am interested in. I do not see an option to enable the scroll wheel, so I hope this functionality has not been permanently removed and it is truly a bug.
Settings -> time zones -> see checkbox on end.
ugh, now I feel stupid. I thought I looked everywhere.
np