lightdm session-cleanup-script not working

[ewangi]

In Mint 19.3 MATE, in order to unmount VeraCrypt volumes on logout, I create the file /etc/lightdm/veracrypt-logout.sh, apply chmod +x to it, and populate it with the following:

#!/bin/sh

/usr/bin/veracrypt -fd
pkill veracrypt

I then add the following lines to the start of /etc/lightdm/lightdm.conf:

[SeatDefaults]
session-cleanup-script=/etc/lightdm/veracrypt-logout.sh

This works fine, but the same procedure does not work on Mint 20. It is slightly different on Mint 20 because /etc/lightdm/lightdm.conf does not exist by default so I have created it instead. When this didn't work, I also tried adding the session-cleanup-script line to /etc/lightdm/lightdm.conf.d/70-linuxmint.conf but that did not work either.

By "not working", I mean that the commands in veracrypt-logout.sh appear not to be executed. I am using the same version of VeraCrypt on up-to-date versions of Mint 19.3 MATE and Mint 20 MATE when experiencing this discrepancy between the two versions of Mint.

[xenopeek]

lightdm comes from the Ubuntu focal package base so this sounds upstream. Can you retest on Ubuntu 20.04 LTS and confirm it does work there?

Is there anything in /var/log/lightdm/ logfiles that gives a clue?

Mind that [SeatDefaults] is deprecated. Use [Seat:*] instead. Though I think lightdm still loads [SeatDefaults] section and merges it with [Seat:*].