This new version of the web GUI can now run as a Windows service:
https://acrosync.com/duplicacy-web/duplicacy_web_installer_win64_1.1.0.exe
Run the installer in an administrator DOS prompt, select Install for All Users, and you’ll see the option to install the service at the last step.
Or you can run this command in an administrator DOS prompt after the program has been installed:
\path\to\duplicacy_web_win_x64_1.1.0.exe -install-service
A new service, named Duplicacy Web Edition, will be installed and started automatically.  You can then open the web browser at 127.0.0.1:3875.
With the service installed you’ll find settings and logs under C:\ProgramData\.duplicacy-web.
To uninstall the service, use the -uninstall-service option.
\path\to\duplicacy_web_win_x64_1.1.0.exe -uninstall-service