What are the open source Android applications that allow you to use your own server instead of the cloud and encrypt information at the same time?

Question

Android

I guess I’m not the only one who doesn’t want to trust my private information (organizer, notebook, GPS tracker for running, all that) who the hell knows who, I don’t want it to be stored on other people’s servers (whatever their reputation) to be transmitted in an unprotected form, etc. In this regard, thoughts about writing my own bicycles began to appear, but as soon as I realized this, the question naturally arose if this already exists in finished form.

Answer 1

https://ru.wikipedia.org/wiki/OwnCloud
https://duckduckgo.com/?q=owncloud+site%3Ahabrahabr.ru

ownCloud is a free and open web application for data synchronization, file sharing and remote storage of documents in the "cloud".
Desktop clients are available for direct synchronization of data from PCs running Windows, Mac OS or Linux, as well as mobile devices on iOS and Android. More importantly, the saved data is accessible using OwnCloud's web interface in any web browser.
Features
File storage using conventional directory structures, or using WebDAV
Cryptography
Synchronization between clients running Windows (Windows XP, Vista, 7 and 8), Mac OS X (10.6 and later) or Linux
Calendar (same as CalDAV)
Task Scheduler
Address book (also as CardDAV)
Streaming media (using Ampache)
User and group administration (using OpenID or LDAP)
Sharing content between groups or using public URLs
Online text editor with syntax highlighting and folding
Bookmarks
URL shortening engine
Photo gallery
PDF viewer (using PDF.js)
ODF file viewer ( .odt, .odp, .ods)
Logging module

Answer 2

Offhand - ghost commander + sftp plugin?
What else do you need, backup automation?