This is a known qt5-base issue [1], especially on gnome-wayland. The qgnomeplatform theme, which provides uniform look for QT and GTK apps, doesn't support GTK3 wayland compositor.
As temporary workaround, you can tell GTK3 library to use x11 backend (GDK_BACKEND=x11) or by installing qt5ct package and setting QT_QPA_PLATFORMTHEME variable to qt5ct. [1] https://bugs.archlinux.org/task/50013
