Sorry for reviving an old thread, but I just had a little trouble myself getting Duplicati to work on Manjaro. Also it seems I can’t edit the wiki at post 2 (I’m a brand new user here, so it makes sense).
I’m on XFCE, but I assume the steps I did will work regardless of DE:
The graphical install left me searching in vain for a menu item or trying to start from terminal using duplicati. Installing from terminal instead with pamac build duplicati2-beta provided some information not shown by the graphical installer:
* UI can be accessed via following URL: http://localhost:8200
* Running duplicati user instance (using current user account)
- to reload user systemd modules: systemctl --user daemon-reload
- to start duplicati manually: systemctl --user start duplicati
- to autostart duplicati on user login: systemctl --user enable duplicati
So running those 3 commands post-install got me started.
I do not know if the package duplicati-latest is any different in content from the beta2. Also, I posted the same info at Installing Duplicati - for beginners - AUR - Manjaro Linux Forum