gtk3, gtk4 (probably?) qt, qt in flatpak, gtk3 in flatpak, gtk4 in flatpak (probably)... I'm just not fighting it anymore
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Community icon by Alpár-Etele Méder, licensed under CC BY 3.0
I find KDE works well with GTK3 and below, but GTK4 apps are set to ignore themes, which is a design decision on the GTK4 side. They invariably look completely odd and out of place as they often force the entire Gnome app UI as well as an unalterable theme.
And then Flatpaks also don't generally follow system themes as they're so sandboxed (although there are some work arounds, including making them consistent as flatpaks or allowing them access to the system theme folders to pick up themeing).
But anecdotally I've not had the level of title bar variability on KDE as that screenshot. Although admittedly I do tend to actively avoid Gnome apps as I don't like the design philosophy.