Sadly my old Drobo, which runs a proprietary franken linux variant has a limited selection of built software, not including Duplicati. Sad, since my research pointed me at your kit as being the best solution for my requirement. I have not been disappointed.
Rather than rolling up my sleeves and diving in the deep-end of trying to build Duplicati for the Drobo – if some dev/build guru wants a challenge … Setup a Cross-Compile Environment for Drobo [drobo @ jhah]
I am happy to test the build
I decided to take the easy way out and wrap the Drobo in a computer. For my needs, the cheapest feasible hardware I could get was an orangepi zero 256K. This is the bottom end of the ARM market and some recommend Odroid SBCs that are considerably more robust. I have used RPI SBCs headless servers and have lots of linux admin experience. I felt that getting Duplicati up and running should be trivial. It was, mostly, but with a few gotchas that come with life on the bleeding edge. I am documenting as I go and will post details to an appropriate forum later.
As I write the archive on the drobo is being writted to the cloud using the command line. It has been running without complaint for just under 100 hrs loading 35 to 40 G per day to my b2 bucket using about 40% of the available 10 Mbps upload pipe. That’s good enough for what I need and way more than I am going to need often. It also is kind to the other network users.
In any case, the machine is not straining – with a load of 2-2.5 on the 4 cpus, and 125M memory / 45M swap charges. The cpu temps are holding steady at 65 degrees with no heat sink and no case.
Perfect. Thanks for the memories 
Randy
P.S. a shout out to the community and in-particular – the ARM thread ARM-based Backup Appliance? which should be referenced in the official documentation.