NextCloud

Nextcloud is a suite of client-server software for creating and using file hosting services. Nextcloud application functionally is similar to Dropbox. Unlike Dropbox, Nextcloud does not offer off-premises file storage hosting. Nextcloud is free and open-source, which means that anyone is allowed to install and operate it on their own private server devices.
In contrast to proprietary services like Dropbox, Office 365 or Google Drive, the open architecture enables users to have full control of their data.
The original ownCloud developer Frank Karlitschek forked ownCloud and created Nextcloud, which continues to be actively developed by Karlitschek and other members of the original ownCloud team.