The Xiaomi 14 Ultra could end up using an ultrasonic fingerprint scanner. Many other flagships already use this tech. Samsung is, as well as OPPO, and a number of other companies. Xiaomi hasn’t done it for a long time, since the Xiaomi 5s. Optical under-display fingerprint scanners are still used by the vast majority of smartphone OEMs. Those fingerprint scanners are less secure and inferior in terms of technology. Nonetheless, the level of security is extremely high.