If you are a beta tester, you can check whether it is available on your device or not by visiting WhatsApp settings > Chats> Chat backup> End-to-end encrypted backup.
While using WhatsApp Encrypted Chat Backup make sure to turn off device backup for WhatsApp app. This is important, otherwise the chats that will be saved on your iPhone will not be encrypted. To do this, go to Settings> Your Name> iCloud> Manage Storage> Backup> Disable WhatsApp.
Also, it is important to keep in mind that when using encrypted chat backups, you need to remember the password to decrypt your chat backups. You will need to choose a password that will be used to encrypt future backups. The password will be required when you restore a backup. It can contain numbers and lowercase letters between ‘a’ and ‘f’. If you forget your password, there is no way to decrypt the chat backup.
WhatsApp previously deployed encrypted chat backups on Android for beta users. Once the feature becomes available to iOS beta users, we can expect WhatsApp to roll out the same for all users very soon.
Meanwhile, WhatsApp recently rolled out support for users to move their WhatsApp history from iOS to Android. As of now, support for this feature has been enabled for Samsung branded Android devices running Android 10 or higher. However, WhatsApp has announced that the same will be available for other Android phone users as well.