just a few comments on the products mentioned before:
- Duplicati slowness on larger datasets: I can confirm this from my test on OMV and Windows 10 platform
- Restic has a nice cross-platform GUI version, see the announcementin the Restic forum and more details from Relica
- Duplicacy has a nice cross-platform GUI version which resides "on top" of the CLI version
- GUI for Rclone: yes, the long awaited but unfortunately still in early stage resulting of GSOC project of last year I think. So I do operations on my cloud storage like delete files/folders, rename, make directory etc in a quick and reliable way with Cyberduck and hoping that Rclone finds a way to improve the GUI. I would not mind to pay for a GUI version of it so that also not that tech-savvy users could use it.