I’ve noticed that 3rd party cloud providers are not what I consider to be first-class citizens. For example, I can’t specify a Dropbox folder as the Safari download folder. Nor can I link a folder from Dropbox into one of the text editor apps (
Both of these I can do with iCloud Drive. Is this because Dropbox doesn’t implement APIs or Apple does allow this functionality with 3rd party cloud providers.
It’s possible to specify other providers if they fully support Apple’s document provider technology.
Working Copy is the only provider I’m aware of that has that level of support.
The lack of other supporting providers I understand is both an Apple issue (in making it difficult to do) and those providers preferring that you use their apps, rather using Files.
With iOS 13 they added the ability to download files from Safari. You can go into the settings app under the Safari section to set which folder within iCloud the downloads will go to.