I am using arch Linux with gnome 3.26.2 and x11.
In previous versions of gnome I could use gnome's settings to assign a shortcut to
Ctrl+Shift+Esc, but not anymore.
xev prints the lines below when hitting this combo:
FocusOut event, serial 38, synthetic NO, window 0x3400001, mode NotifyGrab, detail NotifyAncestor FocusIn event, serial 38, synthetic NO, window 0x3400001, mode NotifyUngrab, detail NotifyAncestor
showkey -a does not print anything when hitting this combination.