Today I learned that LineageOS provides SeedVault, an Android Backup app, that lets you backup your phone to a local storage device or cloud provider of your choice, given it implements the right Android API. The Nextcloud app does so and allows the “regular” Android backups, you might know form stock ROMs, which usually end up on Google Drive, to end up on your Nextcloud instead. Of course, properly encrypted with a 12 words passphrase that you should note down.
I came across this while scrolling through my Android settings in order to do an update. Previous times, the Backup options in the settings menu were rather useless, but today I figured out I could setup the Backup with Nextcloud and really enjoyed the experience.