Earlier quoted context omitted.
For the super paranoid, SyncThing provides a straightforward way for you to synchronise your database between various local devices without having any data in the cloud at all. [edit: Syncthing's Discovery Server probably counts as data, actually; you can work around that but then it's less "straightforward"]
OMG I tried to setup SyncThing a couple of months ago to sync my KeePassX (kdbx) between my PC, my MAC and my Android phone. It was hell, I had to fight SyncThing every step of the way (connecting between clients, which one is the receiver and which one is the sender and whatnot), and it just didn't sync. In addition I learned that in Android SyncThing cannot sync to an external SD card ( https://github.com/syncthing…
Besides my general distrust of Google, the real source of my headache is the ransomware attack. Thus such a simple schema is unsatisfactory. And the proper automatic backup procedure needs noninteractive testing whether the cloud copy is not garbled. Until now I don't know how to do it so I make backups of my Dropbox copy by hand.