This is a root/flash/unbrick guide for Nubia devices i have laying around and comes with absolutely no warranty.
The steps are partially tested, partially recreated from what i remember worked for me, use at your own risk.

Table of contents:

• Red Magic (general)
• Red Magic 9 Pro specific
• Red Magic 8 Pro specific

Prepare

Download tools

• Download the factory firmware (see repo files for links)
• Download fastboot enhance
• Download adb/fastboot executables
• Download pathAdder (makes terminal commands easier)
• Download magisk app

Getting fastboot drivers ready

• Boot (any) phone into fastboot by holding power + vol down keys until a screen with text appears
• Go to device manager in windows, you will see an unknown Android Device
• Right click it -> update driver -> browse my pc -> let me pick -> Android -> Android Bootloader Interface

Extracting the partitions

• Extract payload.bin from the factory zip
• Open FastbootEnhance.exe
• Payload Dumper -> Browse -> payload.bin
• Choose
  • boot
  • init_boot
  • system
  • vendor
• Click extract image (may take a while, wait for the pop-up)

Extract fastboot tools

• Pick a location where the folder can stay permanently
• Extract the platform-tools.zip there
• "Install" AddToPath.reg by double clicking it
• Right click the extracted adb folder and Add To Path
• Now you can just run adb and fastboot from anywhere

Create magisk patched boot

• Install Magisk.apk on your or any other phone
• Put the init_boot.img on said phone
• Click patch manually and choose that init_boot.img
• Copy the magick_patched_filename.img to pc

Red Magic (general)

Get Phone status

• Boot phone into fastboot by holding power + vol down keys until a screen with text appears
• Connect phone to PC and open a terminal
• fastboot getvar all to get the current device state, including information like

  • slot-unbootable:a/b:yes/no
    slot-successful:a/b:yes/no
    current-slot:a/b
    

Disable any app (user && system)

• Connect phone to PC and open a terminal
• List packages using adb shell pm list packages or filter using
  • adb shell pm list packages -s: To list only system packages.
  • adb shell pm list packages -3: To list only third-party packages.
  • adb shell pm list packages -d: To list only disabled packages.
  • adb shell pm list packages -e: To list only enabled packages.
  • adb shell pm list packages [filter]: To list packages that contain the 'filter' string in their package names.
• Disable any package using adb shell pm disable-user --user 0 PACKAGENAME
  • Can also disable apps, which are not disbleable in the UI, like crucial system apps, so be cautious

Unbricking the device

• Boot phone into fastboot by holding power + vol down keys until a screen with text appears
• Follow one of the next two methods

Switching slots (quick and dirty way)

• fastboot getvar all
• Check if the slot you are not on is
  • slot-unbootable:no and
  • slot-successful:yes
• fastboot --set-active=<slot_you_are_not_on> and replace <slot_you_are_not_on> with a or b
• Phone should boot successfully into the switched slot, but now the other slot will be broken and it is recommended to fix it

Flashing an OTA (sideload)

This may require a factory reset/data wipe afterwards

• From Fastboot menu, choose to boot into recovery
• A white screen will appear with a green button, don't click anything
• adb devices should show a sideload device
• adb sideload .\NX729J-update.zip will upload and flash the OTA

Troubleshooting

Connection issues

If your fastboot recognizes your device on fastboot devices but fails to flash anything like this:

PS C:\Red Magic 8 Pro\Root> fastboot flash init_boot .\init_boot_4_28_magisk_patched.img
Sending 'init_boot_a' (8192 KB)                    FAILED (Write to device failed in SendBuffer() (no link))
fastboot: error: Command failed

Then check your cable and try using the red usb c cable that came with the phone.

Persist custom launcher as default

Nubia's Red Magic 8 Pro has a default launcher bug. You get a third party one, Set it as default launcher and the phone reverts it back to Nubia's launcher randomly. The Workaround described here is configuring tasker and Autotools, so the global setting default_home is overwritten with the name of the desired launcher in an interval of 1 second. This way, whenever nubia launcher decides to fuck up again and set itself as the default launcher unexpectedly, it will take max 1 second to have your desired launcher as default again. I used this method now for a month and never saw the nubia launcher again.

Requirements

• Root permissions
• Tasker (App)
• Autotools (App, Tasker Plugin)
• Termux (App)
• Lucky Patcher (App), if UI preferred for systemizing an App

Instructions

• Install mentioned apps from Requirements
• Turn Autotools into a system app using either a) or b) (Autotools needs the permission to WRITE_GLOBAL_SETTINGS, which is exclusive to system apps)
  • a) Open Lucky Patcher, grant root, search for Autotools and turn it into a system app
  • b) Use Termux to make it a system app by essentially moving it from data/app to system/app (Google how to do that)
• Reboot and check if Autotools is now a system app
• Execute the following commands in Termux:
  • su
  • pm grant com.joaomgcd.autotools android.permission.WRITE_GLOBAL_SETTINGS
• Open Tasker and create a task, I called mine OnInterval (Every Second)
• Add a new action by clicking (+)
• Search for autotools secure settings and choose it
• Configure it to use the following data (replace value with your launchers package name):

Setting Type: Secure
Name: default_home
Input Type: String
Value: com.microsoft.launcher
Read Setting: true

• Go back and create a new profile, I named mine OnInterval (Every Second)
• As Trigger, choose Event, search for "Tick" and set it to 1000 (Mm, so I lt runs every second)
• As action, take the one just created
• Done

Red Magic 9 Pro

Unlocking the bootloader

Unlocking the bootloader on this device is (currently?) not possible, as the commands fastboot flashing unlock and fastboot oem unlock are reported to be unknown by the device in fastboot mode. They probably removed these from the bootloader, but it should be possible to patch the bootloader to know these commands. There is a reddit post on this. The bootloader was disassembled, probably using ghidra to search for strings and no unlock command was found.

Red Magic 8 Pro

Unlocking the bootloader

Rooting with a password/pin/fingerprint already set up will break the lockscreen afterwards, but not irreversibly. However, to make sure everything works while unlocking, make sure to remove all of these (or simply do a factory reset).
There is an XDA guide on this
Summed up:

• Backup any data on your phone, it will be wiped
• Have a locked bootloader
• Remove any protection (pin/password/fingerprint) by e.g. doing a factory reset (Power + Volume down, until recovery shows up)
• Developer options -> turn allow OEM unlock on
• Reboot into fastboot mode using adb reboot bootloader
• Unlock the booatloader using fastboot flashing unlock
• And the "critical" one using fastboot flashing unlock_critical

Rooting (flash a patched magisk boot image)

• Install and open Magisk app on your or any working android phone
• Upload the init_boot.img to said phone
• Choose patch image and choose the init_noot.img
• A patched image will be located in /Download, transfer that to the host pc
• fastboot flash init_boot ./magisk_patched_something.img will flash it to the currently active slot
• fastboot reboot