LineageOS
There is official documentation available:
https://wiki.lineageos.org/devices/polaris/
The installation steps are relatively simple; first, flash the specified MIUI version, and then flash LineageOS, and it should work fine.
However, the official site only provides the latest version (Android 15) image, and higher versions of Android tend to crash during debugging with IDA 7.7. I am not sure how IDA 8.3 performs.
Other lower versions I found are unofficial, compiled user-debug versions, and you need to install GApps yourself, which is a bit troublesome.
PixelExperience
The official site provides images for versions 12 – 13. However, I want to flash version 10, as my Pixel is on 10, and I have no compatibility issues with IDA 7.7.
I found a cloud drive:
https://share.zimiao.moe/ROM-01/小米MIX2S
It contains the Android 10 version.
Since my phone was previously flashed with LineageOS, I no longer have recovery, so I cannot follow the instructions in the documentation (https://wiki.pixelexperience.org/devices/polaris/install/). I can only force flash it using the sideload method. During the process, it will prompt for signature mismatch, which I can ignore, and after flashing, it boots normally.
Run: adb -d reboot sideload
Run: adb -d sideload /path/to/zip
The only issue is that the com.android.phone application frequently crashes. Initially, I thought about flashing Magisk to remove this app since I don’t need it, but after flashing Magisk, the crash stopped occurring, which is quite strange.