MATE expects DESKTOP_SESSION to be set to mate, not MATE which can be seen by inspecting /etc/X11/xinit/xinitrc.d/ for mate 10-user-dirs-update-mate, 10-xdg-menu-mate and 15-xdg-data-mate all have: if [ "$DESKTOP_SESSION" = "mate" ]; then Can be worked around in Xsession using: Convert MATE to lower case as MATE scripts expects this [ "$DESKTOP_SESSION" = "MATE" ] && DESKTOP_SESSION=mate export DESKTOP_SESSION
I think this should be reassigned to MATE instead. MATE should test for both "mate" and "MATE" so we don't have to fix every random DM
I am closing this as I think MATE should use XDG_CURRENT_DESKTOP instead