How to disable dead keys

I have a Debian 11 box running the Cinnamon DE. My keyboard layout is, per localectl status:

System Locale: LANG=en_GB.UTF-8
       VC Keymap: uk
      X11 Layout: gb
       X11 Model: pc105

while $GTK_IM_MODULE is ibus. My problem is that this setup has *dead keys* enabled and I really don't want that. My question: what must I change to turn dead keys off? Strange observation: I have a second debian-11 machine which runs emacs EXWM as window manager and the exact same keyboard setup (as far as I can see) and here I have no dead keys exactly as I want. Does the desktop environment impact this issue?