As per the latest information revealed by WABetaInfo, WhatsApp has now started rolling out the 23.24.70 update for iOS on the App Store, which brings the additional verification method.
WhatsApp Email address verification is now available
WABetaInfo claims that the feature is rolling out widely and we can safely assume that the rollout is being carried out in a phased manner.
WhatsApp relied only on phone numbers and OTP SMSes to verify and authenticate users. Users can head to Settings > Account > Email Address. Once users enable the feature, they will be able to get the 6-digit code through email instead of SMS.