Even if I hate its looks, but LibAdwaita is more and more adopted to migrate GTK3 apps to GTK4, many known apps already embraced it like: EasyEffects, Foliate… Even Xournal++ started migrating to it. And some of them like EasyEffects has no similar alternative in terms of features and quality of audio output.
After testing Gradience with Dark Breeze preset, it seems to do pretty well at unifying at least the colors:
So why not integrate this addition into Plasma 6 settings to widen the coverage of Breeze theme to also include LibAdwaita apps.