KPackage Manager: install, list, remove Plasma packages. More information: https://manned.org/kpackagetool6.
kpackagetool6 --list-types
kpackagetool6 {{[-t|--type]}} {{package_type}} {{[-i|--install]}} {{path/to/directory}}
kpackagetool6 {{[-t|--type]}} {{package_type}} {{[-u|--upgrade]}} {{path/to/directory}}
--global for all users):kpackagetool6 {{[-t|--type]}} Plasma/Applet {{[-l|--list]}} {{[-g|--global]}}
kpackagetool6 {{[-t|--type]}} Plasma/Applet {{[-r|--remove]}} "{{name}}"