Yes this seems like a robust solution that is very close to what I want. I think that in this case DropBox can be replaced with RClone that syncs to a few different clouds in a loop once every say 10 sec - from a bash script or something. The thing is it’s not only about not uploading your data open to the cloud provider. It’s also about not installing a black box non open source app that is running in the background at all times.