Xiaomi has started rolling out Android 12 to the Mi 11, Mi 11i and the Mi 11 Ultra. Currently, Google's new OS is available for Mi Pilot testers on MIUI's global branch. Xiaomi considers the updates Stable Beta builds.
https://www.notebookcheck.net/Mi-11-Mi-11-Ultra-and-Mi-11i-start-receiving-Android-12-Stable-update.568962.0.html
I just attempted to install the mi 11 ultra rom and now my phone is bricked. I cannot even get it into recovery mode.