For the moment it's better not to update some Xiaomi to Android 12, but if you really want to risk is super recommended a backup of data in memory
There is a lot of curiosity around Android 12, the latest incarnation of the cute little green robot that "lives" inside many smartphones. And it can't be surprising if some, to shorten the wait, have ended up installing and using betas of Android 12, even if beta versions of firmware are usually not very stable.
The firmware that Xiaomi has marked as "stable beta" of Android 12 should have been, so yes a beta but a bit more stable than normal. Maybe it will be during use, as long as you don't end up "breaking" the product to be updated, so before you even use it. This is what happened to several users, who have flocked to the network to report following the update the "brick" of their Xiaomi Mi 11, ie a smartphone that is unable to do anything, not even turn on.
The Xiaomi and firmwares involved
The Android 12 updates that have given rise to sometimes serious problems are those identifiable with the build number 18.104.22.168.SKBMIXM, 22.214.171.124.SKKMIXM and 126.96.36.199.SKAMIXM, respectively, for Xiaomi Mi 11, Mi 11i and Mi 11 Ultra. Of the issues that have affected users, we hear about them thanks to numerous reports on various online discussion channels.
Basically, some of those who trusted the software that Xiaomi identifies as a "stable beta" of Android 12 for Mi 11, Mi 11i and Mi 11 Ultra ended up with a nice paperweight instead of a performance smartphone updated to Android 12, albeit in beta. It turns out that the problems causing near irreversible damage occur during the installation process, and can usually be fixed by entrusting the product to the support network.
Those who have a good experience with technology and a good number of skills can try to solve the problem by themselves, but the final result is not guaranteed and it's necessary to invest several hours in the research of possible solutions to the problem, which don't necessarily work.
The importance of data backup
In short, it's a lot of trouble for a problem for which, in fact, users have no responsibility. Moreover, both the service solution and the DIY resolution attempt imply the loss of data in memory, so those who had underestimated the importance of a pre-update backup find themselves with a double damage.
These are the occasions when you "touch" with your hands the importance of a backup before updating an electronic product: companies, including Xiaomi, always strongly recommend to do it, but the fact that generally software updates don't give problems means that many have lost the habit of making a "preventive" backup, only to regret it in cases like this.
Anyways, it's clear that despite these builds were marked as stable MIUI based on Android 12 they weren't actually stable at all. So watch out for other Xiaomi's to update with this kind of software: better make a backup of your data first.