After updating from MIUI 14 to HYPEROS on my 11 Ultra three weeks ago, I immediately noticed high battery drain. After waiting for like 10 minutes with the screen off to give it a chance to finalize any probable background after-installation actions, I performed a restart. It didn't help. After some time having let the phone without using it, I noticed that the screen was a bit warm, especially near the fingerprint scanner, although it should be cold, meaning that indeed the battery was draining fast. This was also confirmed by the phone itself in the Settings/Battery graph. Then I thought I would minimize battery usage by deactivating Always-On-Display. This did the trick for me. After doing so and letting the screen off for some time, the phone cooled off and the battery drain stopped. I don't know if this is relevant, but disabling AOD seems to have done the trick for me... Since then, the battery drain is normal again.