The Xiaomi 15 Ultra supports Raise to wake.
For your reference, here is more information about the Raise to wake function:
1. It utilizes the phone's accelerometer sensor to achieve. When enabled, it allows your phone's screen to automatically wake up or turn on when you pick up or raise the device and shows your lock screen, notifications, or the time without the need to press any buttons;
2. To enable this feature on your phone, you can go to [Settings] >> find and tap [Lock screen] >> enable [Raise to wake];
3. After the settings are completed, you can turn off the screen and then raise the phone to check if the phone wakes up.