It seems we're still at a stalemate between working GTK <-> Qt themeing and working GTK integration in Telegram: completely removing the patch from libqt5-qtbase predictably brought back bug 1002900, replacing it with a patch that adds GTK2 second also results in QT apps on GTK falling back to the GNOME default theme... https://build.opensuse.org/package/show/home:tux93:branches:KDE:Qt:5.13/libqt5-qtbase