Of course one should avoid using the originally provided GTK software under KDE, as it’s also spamming the app drawer.
It should work the same as for the Ubuntu -> Kununtu transition: Install some KDE Plasma desktop metapackage, logout and login using KDE, then remove the libgtk* packages to uninstall the Mate/Cinnamon desktop and it’s associated applications. One can reinstall the desired packages, e.g. Firefox, Thunderbird, Synaptic, afterwards.
Of course one should avoid using the originally provided GTK software under KDE, as it’s also spamming the app drawer.
It should work the same as for the Ubuntu -> Kununtu transition: Install some KDE Plasma desktop metapackage, logout and login using KDE, then remove the libgtk* packages to uninstall the Mate/Cinnamon desktop and it’s associated applications. One can reinstall the desired packages, e.g. Firefox, Thunderbird, Synaptic, afterwards.