What GNU + Linux software could enable deep integration of backup, sync, and transfer; just as convenient and beginner-friendly (edit: and efficient) as what Apple provides?

For example, iOS has these features:

• iCloud backup restore or peer-to-peer transfer, very early in the device setup process
• Two ways for things to be stored in iCloud, each with a corresponding list of per-app (not per-folder) toggle switches in iCloud Settings
  • "Saved to iCloud" normal syncing
    • Requires apps to use the right APIs and to handle conflicting changes
    • Allows same data to be read and modified by multiple devices
  • iCloud backup
    • Available for all apps
    • Separate backup per device
    • Only downloaded when setting up a new device
    • In app sandboxes, only excludes tmp (Flatpak equivalent is somewhere in /run) and Library/Caches (equivalent to cache directory in Flatpak sandbox) by default
    • Allows apps to set isExcludedFromBackup attribute for specific files (useful for things that are easy to recreate via download but are expected by the user to not be automatically deleted)
    • Includes system configuration such as home screen layout
    • Backs up a list of installed apps without backing up their executables and assets
• Synced list of previously installed apps, not separate per-device