Breeze & Elementary OS icon set for KDE Plasma.
The image is taken from the OpenDesktop-Dark Global Theme (https://store.kde.org/p/1484021), which automatically installs also this icon set.
KDE Plasma users may go to System Settings, Appearance, Icons, Get New Icons..., search for OpenDesktop-Icons and apply it.
Non-KDE Plasma users may download and unzip the compressed file into ~/.icons (create .icons folder if it doesn't exists in your home); then apply it depending on your system (e.g. on Ubuntu use Tweaks)
Based on the following work:
with minor changes.
(included in "OpenDesktop-Dark" KDE Plasma Global theme - https://www.pling.com/p/1484021
if installed via KDE, System Settings, Appearance, Global Theme, Get New Global Themes... button, Search... OpenDesktop-Dark, Install, Apply)