[Huawei Nova 3i Guides, News, & Discussion] darkghost1999:
After quite searching and struggling, I've found a way to install TWRP and Magisk (root) and get it working on my Huawei nova 3i/p smart+ 2019. (At the end I leave info about how I've unlocked bootloader). I am not an expert but I just share what I did. Also, English is not my native language, so I apologize for possible grammatical errors or awkward expressions.

I will leave all the files I've used here:

SomeStuff

MediaFire is a simple to use free service that lets you put all your photos, documents, music, and video in a single place so you can access them anywhere and share them everywhere.

www.mediafire.com

As TWRP does not officially support this phone, I found and used an unofficial modification that seems to work. Here are few steps to install TWRP:

I assume (if not, google search it) you have enabled all features in android settings needed to use adb and fastboot (tools included in the zip file I've provided)

I also assume that you have the bootloader unlocked (some info at the end)

Once your phone is connected via USB to your PC, use the command "adb reboot bootloader" to set the phone into fastboot mode.

Then, with the file "twrp-kirin.img" on the console's directory run the command "fastboot flash recovery_ramdisk twrp-kirin.img".

Finally, run "fastboot reboot"

If everything went okay, a working TWRP should be installed. To enter it, first shutdown your phone. Then hold for near 10 seconds the power and volume up buttons simultaneously, after a while the TWRP screen will show up.

Once TWRP is ready, put the Magisk .apk and Magisk .zip into the external microSD. You will notice that the apk and zip versions are not the lastest; this is intended, as I have only got this version to work. Anyway, later on you can update them easily.

Install Magisk:

Enter TWRP and install Magisk.zip file.

Shutdown your phone and then hold power and volume up buttons as if you are entering TWRP menu. For some reason, this activates Magisk but from now on the access to TWRP is blocked somehow.

Once on the android system, with file manager go to SD card and install the Magiksk.apk

That's it! Magisk is installed, you can check root access with root checker or similar apps.

If you want to update Magisk to last version, you should enter the Magisk manager app and click update app. For updating Magisk itself, select option "recovery" and then "Install directly", then you reboot your phone and that's all.

TWRP is still installed, but as Magisk is installed as well in recovery partition (this phone does not have Ramdisk partition), some conflict blocks TWRP from starting. If for any reason you need to start TWRP, you can uninstall Magisk from the app and then start TWRP with the "hold power and volume up buttons" way.

About unlocking bootloader, I've found a working method provided by DC-unlocker. You will need DCPhoenix and HCU programs and to spend a few bucks (in my case 19€) to get a 3 days license to use the programs. The link to the official web is

Unlock modems, routers and phones with DC-unlocker software

DC-unlocker is universal, fast and easy to use unlocking tool. Supports Huawei, ZTE, Sierra Wireless and other modems, routers and phones.

www.dc-unlocker.com

And they made two tutorials about the matter. If you follow every step carefully it will work:

How to enable software testpoint (required before using HCU new features):

How to unlock bootloader:

Hope that helped and good luck!