I recently discovered Duplicati and I find it really efficient and easy to use but after adding several servers in my backup strategy, I quickly needed a monitoring system. I wanted a self-hosted solution so I created a docker stack to do the job.
You can find it here :
The idea is quite simple and works with 3 components. A Telegraf agent that retrieves reports, a Influxdb database and a Grafana dasbhoard to display a nice view.
You just have to specify to your Duplicati instances to send the backup reports to the agent.
You can find more details in the readme.
Please feel free to use it and fork it if you want.