I’d like to use Cryptomator (I have it on my phone), however it does not support the DocumentProvider API.
Because of this, using files inside a Cryptomator vault is very problematic with some apps. It is only possible to select a file in Cryptomator, and open it in an app. It is not possible to open a folder (unless I missed something).
For example, as far as I know it is impossible to open an Obsidian vault (a folder with markdown files linked between them) in Obsidian, if files are in a Cryptomator vault (and Android). It’s only possible to select one file in Cryptomator, and open it in some app. Same problem with some other apps.
Instead of using files inside the Cryptomator vault, an alternative could be to send a copy of local files in the Cryptomator vault. But because of the lack of the DocumentProvider or automation app support, it does not seems possible to automate this copy…