following DIAGNOSTICS in man page

systemd-cron

systemd generator that provides cron daemon & anacron functionality

This is a generator that dynamicaly translates /etc/crontab, /etc/cron.{d|hourly|daily|weekly|monthly|yearly}/* and user cronjobs into systemd .timer & .service units.
mail/news client with RSS, chat and integrated spam filter support

thunderbird

mail/news client with RSS, chat and integrated spam filter support

Thunderbird is an mail client suitable for free distribution. The goal of Thunderbird is to produce a cross platform stand-alone mail application using the XUL user interface language. It supports different mail accounts, no matter of the used protocol like POP(s) or IMAP(s), has an integrated learning Spam filter, and offers easy organization of mails with tagging and virtual folders. Also, more features can be added by installing extensions.
Plasma extension that monitors the current status of gamemode

plasma-gamemode

Plasma extension that monitors the current status of gamemode

GameMode optimises your system for peak performance when running a game.
Simple offline API documentation browser

zeal

Simple offline API documentation browser

Zeal is a simple offline API documentation browser inspired by Dash (OS X app), available for Linux and Windows.
User interface for controlling the PipeWire Graph

qpwgraph

User interface for controlling the PipeWire Graph

qpwgraph is a graph manager dedicated to PipeWire (https://pipewire.org), using the Qt C++ framework (https://qt.io), based and pretty much like the same of QjackCtl (https://qjackctl.sourceforge.io).
search and read system documentation

khelpcenter

search and read system documentation

KHelpCenter is an application to search and read documentation for applications, modules, libraries, and system utilities.