The DigitalClock applet, but packaged to be added to the desktop where the calendar view with agenda is visible instead of a clock.

The applet includes the agenda underneath the calendar instead of to the left. Applet background has been disabled.

You can add cloud calendars in Korganize. After that... when in desktop edit mode, you can find the configuration button to set in the applet the desired calendars from which to display agenda events.

Original Digital Clock applet source code: https://invent.kde.org/plasma/plasma-workspace/-/tree/master/applets/digital-clock/package?ref_type=heads

History
Version 0.7 - This is a pretty lazy build and has not removed unnecessary code for the target functionality. This is mostly seen in the configuration options. Everything works for me pretty stable though.