The developers of WhatsApp are finally close to enabling chat history migration between Android and iOS devices. The source code of WhatsApp 22.2.74 beta for iOS reveals this.
However, this does not seem to be an easy process. The migration process requires the app to be installed on both devices, and the migration process may take place using a cable or dedicated Wi-Fi connection. In contrast, other messaging apps use Google Drive, iCloud, or their own cloud services to store and sync user data.
As of now, the only official way to sync WhatsApp data between iOS and Android phones is to own a Samsung-made device. The migration is done one way – from iPhone to Samsung via cable and using Samsung’s SmartSwitch app.