Welcome to the forums Gandalf.
You should be able to setup Duplicati to run as a service. This thread looks to cover the process.
Once installed as a service, remove the trayicon from launch and access the GUI via http://localhost:8200/ngax/index.html
EDIT: Forgot to mention, you’ll need to change any icons that you use to launch Duplicati so they have the --no-hosted-server switch.