I've a really old but beloved keyboard that lacks any super/windows/apple/whatever key. Is there any way I can lock my desktop without picking "suspend" from the upper right menu with my mouse? (Super-L does work when I plug in a newer keyboard as a test.) I've tried various combinations of Shift-Ctrl-Alt without luck.
You can change the default shortcut editing the dconf. For example, to set it to Ctrl+Alt+L you can type:
gsettings set org.gnome.settings-daemon.plugins.media-keys screensaver "<Ctrl><Alt>l"