widget themes for GTK4 apps no longer works

[ExecutorElassus]

Previously, I would set my widget theme for GTK apps using lxappearance, and recently I've installed nwg-look to do the same. However, while both of them show a list of available themes, clicking different ones does nothing. I'm not using an integrated WM (I'm using FVWM), so there's no built-in "settings" app to change the look of all apps.

How do I go about setting the widgets theme? I *am* able to change the mouse theme with either lxappearance or nwg-look, just not the widgets theme.

Also, using the commandline