These conflict. First says to put the server at port 8300. Second says to not run server. Which wins?
One way to find out is to browse to port 8300. You want (I assume) only the started-at-boot Duplicati however the started-at-login TrayIcon connects to that other to provide a bit more control and status.
If you don’t need Duplicati running as root, or when you’re not logged in, then take that path instead.
It’s only predicted if you protect your GUI (e.g. using the Settings screen, or –webservice-password).
If this is nothing you made, it’s possible it’s leftover from defaults the AUR packagers have provided.
If password was picked by you, you could try giving TrayIcon --webserver-password=<password>
Have you used systemctl as specified? You can also use ps -ef | grep -i duplicati to watch.
You should have two processes as root (the start-at-boot), and two as you, which will eventually go
away if it can’t get logged in to the server due to the password problem. It will retry connects briefly.