is not intended to reflect Ubuntu GNOME 17.04, but only Ubuntu 17.04 (with Unity). OTOH, neither GNOME Help seems to accurately reflect Ubuntu GNOME 17.04 in this respect; changing the affected packages of this bug.
As you say, the GUI option to set a compose key seems to be gone in Ubuntu GNOME 17.04. Can't tell if it's a bad design decision or if there is some other GUI way which is not (yet) documented. Anyway, you can set it with a terminal command.
To make <RightCtrl> the compose key, run:
gsettings set org.gnome.desktop.input-sources xkb-options "['compose:rctrl']"
To see which other keys are possible to use, enter the terminal command:
man xkeyboard-config
and scroll down to the section "Position of Compose key".
Please note that the Ubuntu Desktop Guide, i.e.
https:/ /help.ubuntu. com/stable/ ubuntu- help/tips- specialchars. html#compose
is not intended to reflect Ubuntu GNOME 17.04, but only Ubuntu 17.04 (with Unity). OTOH, neither GNOME Help seems to accurately reflect Ubuntu GNOME 17.04 in this respect; changing the affected packages of this bug.
As you say, the GUI option to set a compose key seems to be gone in Ubuntu GNOME 17.04. Can't tell if it's a bad design decision or if there is some other GUI way which is not (yet) documented. Anyway, you can set it with a terminal command.
To make <RightCtrl> the compose key, run:
gsettings set org.gnome. desktop. input-sources xkb-options "['compose:rctrl']"
To see which other keys are possible to use, enter the terminal command:
man xkeyboard-config
and scroll down to the section "Position of Compose key".