Comment by treyd

I use CalyxOS and sync with the Nextcloud app to my home server. There is Seedvault built in but I've found it to be slightly janky. Many apps can directly operate on files synced through the Nextcloud app like that, or at least directly export backups to Nextcloud through the file provider APIs. Calendars and contacts are supported through WebDAV apps lile DAVx5.

It pretty much just works with little manual involvement.