Running services as root is not a good practice. In favour of Traccar being deployable as easy as possible, we made the compromise of not tieing Traccar to running as a specific user.
That being said, we highly recommend you do not run Traccar as root user.
You can achive this by adding a systemd Drop-In to the traccar.service. For that, follow these steps:
mkdir /etc/systemd/system/traccar.service.d/ touch /etc/systemd/system/traccar.service.d/run-as-user.conf
The content of the file should set the user for traccar to the one you want to run it as. Keep in mind, that the Traccar directory has, of course, to be readable and writable by that user.
[Service] User=traccar Group=traccar