I remember ~4 years ago, I needed to retrieve an old file, and I discovered that DropBox does write a diff-based repo, which you can restore at different points

I remember ~4 years ago, I needed to retrieve an old file, and I discovered that DropBox does write a diff-based repo, which you can restore at different points. I don't remember the details, but I needed to use some sort of CLI to access/navigate it on the host system. In short, it is probably possible now, using what DropBox already exposes.