iCloud sync
From the app’s English Help & Guide · Reference release 1.0.13
When enabled in More > Data, your own Supported data syncs across your devices via your personal iCloud account. After changing the toggle, Supported shows a restart notice because the SwiftData iCloud store is chosen when the app launches.
Automatic backups are a separate optional choice. Existing iCloud data may take a little while to appear after restart, so keep the app open while it settles.
Data from the person you care for comes through CloudKit shared zones — a different mechanism. This is automatic once you've connected via a share link.
Shared status and profile content is read-only on your side. The only thing Supported writes back is a Between us entry you explicitly choose to post.