Nextcloud is a suite of client-server software for creating and using file hosting services. It is functionally similar to Dropbox, although Nextcloud is free and open-source, allowing anyone to install and operate it on a private server. In contrast to proprietary services like Dropbox, the open architecture allows adding additional functionality to the server in form of applications.
Install Nextcloud via F-Droid - https://f-droid.org/en/packages/com.nextcloud.client/.
The configuration is pretty much self explained. Just start the client and login to your server (https://nextcloud.home).