For specific case of backups, apps on cloudron are already encrypted and backed up automatically to your S3 bucket. This happens at a app level, so you can rest

For specific case of backups, apps on cloudron are already encrypted and backed up automatically to your S3 bucket. This happens at a app level, so you can restore apps individually as well. Though, I think you are asking if we some form data picker between apps. Like ownCloud can expose contacts that can get picked up from some mail app? Most apps these days expose a REST API. For example, GitLab sends notifications to Rocket.Chat via webhooks. I can edit files on ownCloud via webdav from my desktop and my radicale contacts are available via carddav to thunderbird. There's standards in place for each kind of data access and all these go beyond web apps. From what I have seen, even having a simple data-sharing layer require requires modifications to apps and this is a lot of work. Like sandstorm, cozy.io also has a interesting data layer but they simply decided to just make apps of their own mostly I am guessing (just guessing :-) ) the reason is that it is very hard to modify and more importantly convince existing app authors to take their changes upstream.