Safari treats extensions differently from Chromium browsers — they're distributed and enabled through the Mac App Store rather than an in-browser store, and need to be turned on manually in Safari's settings after installing. It's a couple of extra steps, but the result works the same as anywhere else.
Apple requires all Safari extensions to be reviewed and distributed through the App Store, and disabled by default for privacy reasons. This is different from Chrome or Firefox, where installing from the store enables the extension immediately.
iCloud Keychain syncs well across Apple devices but doesn't extend to Windows, Android, or Linux, and has no sharing features for family or team use. A dedicated vault extension covers every platform from one account, with the same unlock experience everywhere.
On iOS, enable the extension under Settings → Safari → Extensions after installing the app. From there it appears as an option in the "..." menu on any Safari login page, letting you fill credentials with Face ID or Touch ID instead of typing your master password each time.
Point it at vault.vpn4all.eu and your vault is live everywhere.