Android 11's stable release is allegedly expected around September 8, but you can take an early glimpse of the upcoming major version of the OS right now through the beta builds. Apart from Google, several OEMs have come forward to offer official Android 11 beta builds for a bunch of smartphones. Xiaomi, for example, initially released vanilla AOSP 11 firmware for the Mi 10, Mi 10 Pro, and the Redmi K30 Pro (Chinese variant of the POCO F2 Pro), but the subsequent builds were rebased on top of the company's MIUI custom skin. The Chinese OEM has now offered a similar treatment to the owners of the Mi Note 10 by releasing a closed beta build of MIUI 12 based on Android 11 Beta 3 for the phone.

Xiaomi Mi Note 10 XDA Forums

Matter of fact, the actual beta firmware is meant for the China-exclusive Mi CC9 Pro. Since the Mi Note 10 and its "Pro" variant are nothing but a rebranded edition of the Mi CC9 Pro (code-name "tucana"), the package itself can be manually sideloaded on the former phone duo as well. Of course, you can't use MIUI's built-in updater for this task, so better opt for a custom recovery solution like TWRP for the flashing job. Moreover, you can’t find Google Play Services or any pre-installed Google apps in this firmware, as such closed beta builds of MIUI 12 are intended for the Chinese userbase.

Download Android 11 Beta 3 with MIUI 12 for the Mi Note 10 / Mi CC9 Pro

Caution: The build mentioned on this page is an early release and never intended to be used as a daily driver. The firmware may contain serious bugs and other system instabilities. It is highly recommended that you backup your data before proceeding. Please exercise your own discretion.

You can download the build from the link below:

To update, download the file and simply use TWRP to flash it. In case you want to downgrade, it would be better to pick the stable Fastboot firmware for your model and do a clean flash.

Thanks to XDA Member kacskrz for providing the download link!