This question already has an answer here:
I have Kali-64bit installed in Virtual Box, and I'm simply trying to set the MATE environment as my default for when I reboot/shutdown and log in afterwards.
update-alternatives --config x-session-manager
and choosing mate-session (be it auto/manual mode) but I still get signed into the default GNOME environment.
Yet when I run update-alternatives command again, MATE is still selected and hasn't reverted back to GNOME.
This should be such a minute command that I've ran on two other Kali installations and it worked flawlessly, yet on my Vbox installations, the update-alternatives just wouldn't stick.