@Hannibal, I see the problem. I told you /usr/lib/triggercmdagent which is the path on Ubuntu, not Raspberry Pi. Sorry about that. I corrected the "next steps" above to match the instructions here.
It should look like this when you run the triggercmdagent command as root:
pi@fe5978dee0e5:~$ sudo su -
root@fe5978dee0e5:~# triggercmdagent
Run installdaemon.sh to install the triggercmdagent daemon so it runs during boot
Daemon install: false
No token exists. Login to request one.
prompt: token:
Then run this to install the background agent that will startup as root during boot:
/usr/share/triggercmdagent/app/src/installdaemon.sh
Then edit /root/.TRIGGERcmdData/commands.json and make sure your commands have ground = background.