@jonas Well in my experience all KDE-related theme stuff are generally behaves rather bad in other DEs, especially in gtk-based environment. And breeze is kde default theme, so it applies too, i guess.

But Qt themes not related to KDE usually behave ok everywhere from my experience. I'm personally using QtCurve configured to mimic my gtk3 Adwaita-dark theme under gnome shell, and it looks fine.

Anyway, what im trying to say is, as long as other qt themes work fine, and breeze works in kde, it should probably be fine. Compared to windows, at least.

p.s. Ok there qt6ct actually, but its only present in fedora and arch official repositories, and not others. For most users its as good as not present, as they probably wont bother trying to compile from github.