[Xiaomi Redmi Note 5 / 5 Plus Guides, News, & Discu] moralesnery:
Thank you for your instructions. I wanted to install a GSI 9.0 ROM since Pie came out, but other threads with instructions were too complex or convoluted that I thought it was harder.

I would like to make some clarifications on your steps:

* I used the unofficial PixelExperience 9.0 GSI image, as you said. It feels and behaves almost exactly as the official PixelExperience build for our device, but with nicer interface. The image is HERE. Just as a sidenote, the System image comes with DPI = 360, things look a bit too big. To make it look like MIUI or the official PixelExperience build for vince, a dpi of 390 should be set (this can be done from settings > System > Developer Settings > Minimal Width, under the "draw" section).

1. Reboot to custom recovery (if you have) flash OrangeFox R8.1 treble-enabled recovery. [If you have already have OrangeFox Recovery skip this step]

2. Touch Wipe and wipe /system /data /cache /dalvik and format /data

* At this step, I had to make "Format Data", and only then reboot to recovery again, and make the wipes to all other partitions. Without rebooting the wipes weren't possible (it was showing errors while trying to mount partitions). VENDOR PARTITION SHOULD NOT BE WIPED

3. Flash cardinal-aosp ROM to your device You do not need to install GApps as we are going to use Pie anyway.

4. After flashing reboot to system it will directly go into launcher without setting stuff up. Reboot your device to recovery again.

At this point, you must check that the hardware works correctly. Touch, screen, audio, BT, wifi, RIL, LTE or whatever you use. If something doesn't work at this point, it won't work after installing the GSI image.

5. Touch install, touch install image and flash the system image you've extracted. Wait for it to complete.

* In OrangeFox, at this point before flashing the GSI's .img file, the recovery asks for the type of image. For noobs and careful people, "System Image" must be selected before proceeding.

5.1 If you installed other than Pixel Experience please install proper GApps right after. [IF GAPPS WONT INSTALL BOOT THE DEVICE INTO SYSTEM FIRST AND WHEN BOOT COMPLETED PLEASE REBOOT RECOVERY AND FLASH GAPPS IT WILL WORK] After GApps installed go to wipe and do a factory reset in recovery. Reboot the device into system.

6. After you set up your device there is several optional operations you can do;

6.1 Root: You can use Magisk v17.1 or above to get root access. [Flash via recovery, if Magisk app wont appear in app menu you can install it from apkmirror safely]

* When installing Magisk through recovery, the framework will be installed, but the APK won't appear in the app list. It must be downloaded separately from https://github.com/topjohnwu/Magisk/releases/download/manager-v6.0.0/MagiskManager-v6.0.0.apk

The following modules are working without issues in my setup:

* Youtube Vanced

* Google Product Sans font

* MagiskHide Props Config

6.2 Modules: Magisk modules like V4A, Unified Hosts Adblock etc. works. [Tested].

6.3 Kernel: You can use Genom Kernel or Dark Ages Tercero kernel. [Tested Dark Ages Tercero, works]

Cast and mirror screen are broken. After choosing a screen to share the phone's screen to, SystemUI will crash. Apps with cast capabilites won't detect Chromecast devices (the cast button won't appear).

Thank you for your help