The command /usr/bin/compton -I 0.04 -O 0.04 -D 10 -m 1.0 -C -f -i 1.0 -e 1.0 -G --vsync none --unredir-if-possible --unredir-if-possible-delay 0 -b does exactly what I want, when I run it from a terminal after booting my system as usual. However, putting this command into autostart, causes Lubuntu to fail loading the graphical environment after boot, i.e. no taskbar appears, no windows can be opened using shortcuts, rightclick on the desktop does nothing, etc. Only the default desktop background remains visible (I haven't changed it), but that's all.
It seems to be completely irrelevant, which of the multiple options for autostarting I use, at least I tried:
The graphical wizard from Preferences -> Default applications for LXSession -> Autostart -> Manual autostarted applications -> Add
Adding the command to
~/.config/openbox/autostartAdding the command to
~/.config/lxsession/Lubuntu/autostartPlacing a
compton.desktopfile in~/.config/autostart/(this works for me with other applications)Using
systemdas explained in this highly related question (works for me with other applications, but gives me exact same error here as described in the question)
I assume that my command is correct, because it does what it should when being run from a terminal after boot is complete, and I assume that my error is not related to my use of autostart, because it works for me just fine with other applications.
I'm also using a freshly set up and updated Lubuntu 16.04 LTS VM under Virtualbox to make sure it does not interfer with other configurations on my productive system.