OwnCloud is a cloud storage, that you can run on your own server.
This weekend I decided to set it up for two reasons: 1) help my mother back up her data, 2) auto-synchronise the pictures that I take on the phone to the computer.
Docker makes it very easy to install. A while ago I configured my server using docker compose, and getting OwnCloud up and running on the server took literally less than 5 minutes, from I got the idea that I wanted to set it up. (Later on I decided to change the config, use another database etc. so that took 15 minutes, and another 45 minutes playing around with the web/desktop/mobile-client(installed via f-droid)).