Hi @fabianluscher, Welcome (late, sorry) to the forum. I can’t verify or not all that you say, but I have just done this. Followed the instructions here and downloaded the boot.zip.
For me the file path is /home/rdl/.config/lxsession/LXDE-pi/autostart
The contents of that file is 3 lines that came from the default, and one that I added:
sketchbook/Show_IP_Address/linux-arm/Show_IP_Address
In the Processing IDE I had already exported the sketch, and in the directory it builds is that file. Not quite sure what it is, it’s not the whole application, just some kind of shortcut. (It works, what I want, at a code club, is something on the screen that shows me the IP address of the Pi.)
Hope this helps.