Nice work! Glad to see it improving so much over a short period. I am interested in how programms based on Qt or gtk/libadwaita will look/ be themed in Cosmic. Are there any news about that?
The toolkit decides how their applications look based on whatever theming engines they use. The desktop doesn’t have control over that. So GTK applications use GTK themes, libadwaita applications use libadwaita themes, libcosmic applications will use libcosmic themes. We’ll try to automatically generate similar-ish GTK/KDE/etc. themes if possible, but it’ll depend by what specs those toollkits support in their theming.
As far as I remember, they said in some reddit post that the theming will be shared.