Qt for Python (PySide/Shiboken)

This is a bit complicated. The theming support is directly baked into the SVGs by using named colors, so there's no need for a separate light/dark icon set. Then, some KDE library injects a plugin into the Qt icon rendering pipeline, that renders the icons according to the system theme and even reacts on theme changes to re-create any icons whenever required. If you run the app on a KDE system and use the platform-provided PySide6 (e.g. by using venv's --system-site-packages switch), it'll automatically work there. Qt bundled with PySide6 wheels doesn't ship the plugin, and thus doesn't re-draw the icons properly.