I wanted to disable ctrl-alt-d and it is surprisingly complicated.

At first I have tried to find it in keyboard settings (gnome-control-center keyboard). There is nothing mapping to ctrl-alt-d.

Then I have tried to disable it using gsettings:

gsettings set org.gnome.desktop.wm.keybindings show-desktop "[]"

It had not effect. Even after trying signing in and out.

Here is what finally has worked:

sudo apt install dconf-editor
dconf-editor

Navigate to /org/gnome/desktop/wm/keybindings/show-desktop and change it there.

It is 2025 and Ubuntu is still magical in some places.