[Redmi Note 8 Pro Guides, News, & Discussion] yayimathrowaway:
A word of caution: I am not a ROM developer for this device, I'm just giving a safe method for flashing GSI to this device. If you decide to flash an unsafe/untested GSI (which is anything other than Havoc OS 2.9 GSI) the resulting outcome is your fault, may that be your phone booting up to the welcome screen of your new ROM or a brick. If you have any questions, please PM me.

1. Unlocking the Bootloader

This is pretty easy.

-Install the Mi Unlock app from here on your PC.

-Go to the Settings app on your RN8P.

-Press About Phone and then press the MIUI version number 7 times or until it says "No need, you are already a developer."

-Go back and scroll down until you see Other Settings. Tap Other Settings and from there tap on Developer Options. From there you should turn on OEM Unlocking and USB Debugging.

-Scroll up and click on Mi Unlock Status. Add your account there and install the ADB and USB drivers for this phone onto the PC that you installed Mi Unlock tool to.

-Connect it to that PC via USB and turn off your phone. Open Mi Unlock. Enter your Mi Account information. Enter fastboot mode by holding Power and Volume Down on your phone until a picture of a rabbit appears.

-Press Unlock on Mi Unlock. Then, the program will either say that your phone is unlocked or that you have to wait 168 or more hours. If it does tell you this, wait until that time is up to press unlock again. Once the program says that your phone is unlocked, you're good to go.

2. Installing TWRP

-There isn't actually any official TWRP Recovery for this device, as you may have noticed. Instead, download the LR TEAM Unofficial TWRP here onto your PC.

-Install Szaki Tools onto your PC here. This is not only a minimal ADB/Fastboot tool but it also contains a graphical interface if you need it.

-Install OpenJDK here if you want to use that graphical interface unless you already have JDK installed.

-If you want to use Szaki Tools Graphical interface, connect your phone to your PC via USB and open the file called XiaomiADBFastbootTools with OpenJDK or something else if you already have something to open JAR files.

-Factory reset your phone by going to My Device in Settings, then going to Backup and Reset and then to Erase All Data. Then, press reset phone at the bottom. Put in your password if you have one and press OK on all of the warnings.

-You will see a loading bar, wait until it is finished and then hold the Power and Volume Down buttons to enter Fastboot before the phone boots up to the welcome screen.

-Open XiaomiADBFastbootTools if you haven't already and click on Select Image. Navigate to the LR TEAM TWRP file you downloaded earlier and flash it to the Recovery Partition using the dropdown next to Flash Image. Flash the image.

-Turn off the phone and then boot into Recovery by holding the Power and Volume Up buttons, releasing the power button when you see the Redmi logo.

3. Installing GSI, Magisk, and GAPPS

-Install your GSI (Havoc OS, Pixel Experience, Lineage OS, install at your own risk, Havoc OS tested and works great), Magisk, and OpenGApps Pico package

-Go back to your phone, which should be in Recovery mode right now if you have followed this guide up to this point. Select Wipe in TWRP and then select Format Data. Type yes and then press the check mark.

-Go back, press Reboot and then Recovery. Hold Power and Volume Up and then release Power once you see the Redmi logo to boot back into Recovery.

-Go to Wipe again, but this time press Advanced Wipe. Select Dalvik Cache, Cache, and System. Swipe right.

-Transfer your GSI, Magisk zip, and GAPPS to your phone after you've finished wiping.

-Flash your GSI and Magisk, and then flash GAPPS. If you get an error while trying to flash GAPPS, it's fine. Just continue on to the next step.

-Press Advanced and then Close AVB 2.0 . Make sure you check both before swiping.

-Press Reboot and then System, and then boot into Recovery again using Power and Volume Up.

-Reboot again into system from there just wait. Your phone will probably reboot by itself once before booting into your new GSI ROM.

-If GAPPS did not flash the first time, boot back into Recovery and go to Wipe.

-Press Advanced Wipe and press Repair or Change File System. Then Flash your GSI, Magisk, and GAPPS again.

You should now have a functioning GSI ROM on your phone!

Please let me know which GSIs work, I've tested Havoc, which works really well in general. I've tried flashing Pixel Experience, PHH Treble, and Resurrection Remix and they did not work for me. I have heard that some people have gotten PHH Treble and Reurrection Remix to work though.