How to properly support multiple icon sets

Nowadays almost every application supports multiple themes. Most present here is a night / dark mode. Changing the look and feel of a Qt application seems to be straight forward and not too difficult at least color wise.

But what about changing the icons on the fly?

My story: I have an application written with Qt (QWidget based) which has QIcons for almost all QActions defined in the .ui file.

What is the Qt way of changing the icons globally without needing to call myAction->setIcon(...) for every QAction?