Comment 16 for bug 2018620

Found it. /etc/xdg/xdg-Lubuntu/autostart/lxqt-picom.desktop (note the different name) provided by the lubuntu-default-settings package. To confirm it's what was starting picom, I renamed it to picom.desktop. To explain this, remember I said before that making one desktop file in $XDG_CONFIG_HOME have the "Hidden=True" key would cause all other desktop files *with the same name* in any other autostart directory to be ignored. Restarted and no picom running.

Why session settings doesn't pick up on this is beyond me. It seems to me we should probably get rid of the file in lubuntu-default-settings since the picom package is already providing it.

Perhaps instead we should have a desktop file in /usr/share/Lubuntu/applications with "NotShowIn=LXQt" so that it doesn't show up in the menu. Of course, vim is in there as is TexInfo, so maybe we don't care?